diff --git a/docs/usage.md b/docs/usage.md
index e783509..010f688 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -182,7 +182,7 @@ This is achieved by having a pair of modules: -
     }
 
     module handle_fastened_assembly(thickness) { //! Assembly with fasteners in place
-        screw_length = screw_longer_than(thickness + insert_length(insert) + 2 * washer_thickness(screw_washer(screw)));
+        screw_length = screw_length(screw, thickness, 2, true, longer = true);
 
         handle_assembly();
 
diff --git a/printed/box.scad b/printed/box.scad
index 6cfa7ff..43bd09d 100644
--- a/printed/box.scad
+++ b/printed/box.scad
@@ -75,9 +75,9 @@ function box_corner_overlap(type) = box_wall(type);
 function box_corner_rad(type) = box_sheet_slot(type) - sheet_slot_clearance / 2 + box_corner_gap(type) + box_corner_overlap(type);
 function box_sheet_r(type) = box_corner_rad(type) - box_sheet_slot(type) - box_corner_overlap(type);
 
-function box_screw_length(type, top) = screw_longer_than(2 * washer_thickness(box_washer(type))
-                                                    + sheet_thickness(top ? box_top_sheet(type) : box_base_sheet(type))
-                                                    + box_corner_gap(type) + box_profile_overlap(type) + box_insert_l(type) - 1);
+function box_screw_length(type, top) =
+    let(s = top ? box_top_sheet(type) : box_base_sheet(type))
+        screw_length(box_screw(type), sheet_thickness(s) + box_corner_gap(type) + box_profile_overlap(type) - 1, washers = 2, insert = true, longer = true);
 
 function box_wall_clearance(type) = box_sheet_slot(type) / 2 - sheet_thickness(box_sheets(type)) / 2;
 function box_margin(type) = box_profile_overlap(type) + box_corner_gap(type); //! How much the bezel intrudes on the specified height
diff --git a/printed/camera_housing.scad b/printed/camera_housing.scad
index 366b8c2..486f8fe 100644
--- a/printed/camera_housing.scad
+++ b/printed/camera_housing.scad
@@ -68,7 +68,7 @@ function cam_screw_length(cam) = let(
     front = cam_front_size(cam),
     screw = pcb_screw(camera_pcb(cam)),
     nut = screw_nut(screw)
-    ) screw_longer_than(front.z + washer_thickness(screw_washer(screw)) - nut_trap_depth(nut) + nut_thickness(nut, true));
+    ) screw_length(screw, front.z - nut_trap_depth(nut), 1, nyloc = true, longer = true);
 
 function hinge_z(cam) = cam_screw_length(cam) - hinge_r;
 
@@ -344,9 +344,8 @@ module camera_fastened_assembly(cam, thickness, angle = 0) {
     camera_bracket_position(cam)
         camera_bracket_screw_positions(cam) {
             nut = screw_nut(bracket_screw);
-            washer = screw_washer(bracket_screw);
             t = bracket_thickness(cam);
-            screw_length = screw_longer_than(thickness + t + nut_thickness(nut, true) + 2 * washer_thickness(washer));
+            screw_length = screw_length(bracket_screw, thickness + t, 2, nyloc = true);
             vflip()
                 translate_z(thickness)
                     screw_and_washer(bracket_screw, screw_length);
diff --git a/printed/corner_block.scad b/printed/corner_block.scad
index 9c8f777..aed34fa 100644
--- a/printed/corner_block.scad
+++ b/printed/corner_block.scad
@@ -133,12 +133,10 @@ assembly(str("corner_block_M", 20 * screw_radius(screw))) {
 module fastened_corner_block_assembly(thickness, screw = def_screw, thickness_below = undef, thickness_side2 = undef, name = false, show_block = true, star_washers = true) { //! Printed block with all fasteners
     thickness2 = !is_undef(thickness_below) ? thickness_below : thickness;
     thickness3 = !is_undef(thickness_side2) ? thickness_side2 : thickness;
-    washer = screw_washer(screw);
-    insert = screw_insert(screw);
-    function screw_length(t) = screw_shorter_than((star_washers ? 2 : 1) * washer_thickness(washer) + t + insert_length(insert) + overshoot);
-    screw_length = screw_length(thickness);
-    screw_length2 = screw_length(thickness2);
-    screw_length3 = screw_length(thickness3);
+    function screw_len(t) = screw_length(screw, t + overshoot, star_washers ? 2 : 1, true);
+    screw_length = screw_len(thickness);
+    screw_length2 = screw_len(thickness2);
+    screw_length3 = screw_len(thickness3);
 
     if(show_block)
         corner_block_assembly(screw, name) children();
diff --git a/printed/door_hinge.scad b/printed/door_hinge.scad
index 87b5ed8..a9a665f 100644
--- a/printed/door_hinge.scad
+++ b/printed/door_hinge.scad
@@ -136,8 +136,7 @@ module door_hinge_assembly(top, door_thickness = 6) { //! The moving assembly th
     dir = top ? -1 : 1;
     pin_x = door_hinge_pin_x();
     pin_y = door_hinge_pin_y();
-    washer = screw_washer(screw);
-    screw_length = screw_shorter_than(thickness + door_thickness +  washer_thickness(washer));
+    screw_length = screw_length(screw, thickness + door_thickness, 1);
 
     translate([0, pin_y - (thickness + door_thickness / 2), dir * width / 2]) {
         rotate([90, 0, 180])
@@ -148,20 +147,20 @@ module door_hinge_assembly(top, door_thickness = 6) { //! The moving assembly th
                 screw_and_washer(screw, screw_length);
     }
 
-    translate([pin_x, pin_y, top ? 0 : -washer_thickness(screw_washer(pin_screw))])
-        washer(screw_washer(pin_screw));
+    washer = screw_washer(pin_screw);
+    wt = washer_thickness(washer);
+    translate([pin_x, pin_y, top ? 0 : -wt])
+        washer(washer);
 
-    translate([pin_x, pin_y, top ? washer_thickness(screw_washer(pin_screw)) + stat_width : width])
-        screw_and_washer(pin_screw, screw_longer_than(2 * washer_thickness(screw_washer(pin_screw)) + width + stat_width));
+    translate([pin_x, pin_y, top ? wt + stat_width : width])
+        screw_and_washer(pin_screw, screw_length(pin_screw, width + stat_width, 2, longer = true));
 }
 
 module door_hinge_static_assembly(top, sheet_thickness = 3) { //! The stationary assembly
     dir = top ? -1 : 1;
     pin_x = door_hinge_pin_x();
 
-    stat_washer = screw_washer(stat_screw);
-    stat_nut = screw_nut(stat_screw);
-    stat_screw_length = screw_longer_than(thickness + sheet_thickness + 2 * washer_thickness(stat_washer) + nut_thickness(stat_nut, true));
+    stat_screw_length = screw_length(stat_screw, thickness + sheet_thickness, 2, nyloc = true);
 
     translate([pin_x, 0, -dir * (stat_width / 2 + washer_thickness(screw_washer(pin_screw)))])
         rotate([90, 0, 0]) {
@@ -169,9 +168,10 @@ module door_hinge_static_assembly(top, sheet_thickness = 3) { //! The stationary
 
             door_hinge_stat_hole_positions() {
                 screw_and_washer(stat_screw, stat_screw_length);
+
                 translate_z(-thickness - sheet_thickness)
                     vflip()
-                        nut_and_washer(stat_nut, true);
+                        nut_and_washer(screw_nut(stat_screw), true);
             }
         }
 }
diff --git a/printed/door_latch.scad b/printed/door_latch.scad
index 0172710..d695ebb 100644
--- a/printed/door_latch.scad
+++ b/printed/door_latch.scad
@@ -61,7 +61,7 @@ module door_latch_assembly(sheet_thickness = 3) { //! The assembly for a specifi
     washer = screw_washer(screw);
     nut = screw_nut(screw);
 
-    screw_length = screw_longer_than(height - nut_trap_depth + sheet_thickness + 2 * washer_thickness(washer) + nut_thickness(nut, true));
+    screw_length = screw_length(screw, height - nut_trap_depth + sheet_thickness, 2, nyloc = true);
 
     translate([0, -height - washer_thickness(washer)])
         rotate([-90, 0, 0]) {
diff --git a/printed/fixing_block.scad b/printed/fixing_block.scad
index 78c2db4..3611af9 100644
--- a/printed/fixing_block.scad
+++ b/printed/fixing_block.scad
@@ -122,9 +122,7 @@ assembly(str("fixing_block_M", 20 * screw_radius(screw))) {
 
 module fastened_fixing_block_assembly(thickness, screw = def_screw, screw2 = undef, thickness2 = undef, show_block = true, star_washers = true) { //! Assembly with fasteners in place
     module fb_screw(screw, thickness) {
-        washer = screw_washer(screw);
-        insert = screw_insert(screw);
-        screw_length = screw_longer_than((star_washers ? 2 : 1) * washer_thickness(washer) + thickness + insert_length(insert));
+        screw_length = screw_length(screw, thickness, star_washers ? 2 : 1, true, longer = true);
 
         if(thickness)
             translate_z(thickness)
diff --git a/printed/flat_hinge.scad b/printed/flat_hinge.scad
index 19d8c06..8c4fc17 100644
--- a/printed/flat_hinge.scad
+++ b/printed/flat_hinge.scad
@@ -155,9 +155,7 @@ module hinge_fastened_assembly(type, thickness1, thickness2, angle, show_hinge =
         hinge_assembly(type, angle);
 
     screw = hinge_screw(type);
-    washer_t = 2 * washer_thickness(screw_washer(screw));
     nut = screw_nut(screw);
-    nut_t = nut_thickness(nut, true);
     t = hinge_thickness(type);
     kr = hinge_knuckle_dia(type) / 2;
 
@@ -165,7 +163,7 @@ module hinge_fastened_assembly(type, thickness1, thickness2, angle, show_hinge =
         if(thickness)
             hinge_screw_positions(type) {
                 translate_z(t)
-                    screw_and_washer(screw, screw_longer_than(t + thickness + washer_t + nut_t));
+                    screw_and_washer(screw, screw_length(screw, t + thickness, 2, nyloc = true));
 
                 translate_z(-thickness)
                     vflip()
diff --git a/printed/foot.scad b/printed/foot.scad
index fe8da82..d55a3e3 100644
--- a/printed/foot.scad
+++ b/printed/foot.scad
@@ -69,10 +69,9 @@ module foot(type = foot) { //! Generate STL
 
 module foot_assembly(t = 0, type = foot, flip = false) { //! Assembly with fasteners in place for specified sheet thickness
     screw = foot_screw(type);
-    washer = screw_washer(screw);
     nut = screw_nut(screw);
     squeeze = 0.5;
-    screw_length = screw_longer_than(foot_thickness(type) + t + 2 * washer_thickness(washer) + nut_thickness(nut, true) - squeeze);
+    screw_length = screw_length(screw, foot_thickness(type) + t - squeeze, 2, nyloc = true);
 
     vflip() explode(15, true) {
         stl_colour(pp4_colour) foot(type);
@@ -146,9 +145,7 @@ assembly("insert_foot") {
 
 module fastened_insert_foot_assembly(t = 3, type = insert_foot) { //! Assembly with fasteners in place for specified sheet thickness
     screw = foot_screw(type);
-    washer = screw_washer(screw);
-    insert = screw_insert(screw);
-    screw_length = screw_shorter_than(insert_length(insert) + t + 2 * washer_thickness(washer));
+    screw_length = screw_length(screw, t, 2, insert = true);
 
     explode(-10) insert_foot_assembly(type);
 
diff --git a/printed/handle.scad b/printed/handle.scad
index 53bfb38..881fc60 100644
--- a/printed/handle.scad
+++ b/printed/handle.scad
@@ -91,7 +91,7 @@ assembly("handle") {
 }
 
 module handle_fastened_assembly(thickness) { //! Assembly with fasteners in place
-    screw_length = screw_longer_than(thickness + insert_length(insert) + 2 * washer_thickness(screw_washer(screw)));
+    screw_length = screw_length(screw, thickness, 2, true, longer = true);
 
     handle_assembly();
 
diff --git a/printed/pcb_mount.scad b/printed/pcb_mount.scad
index d6e3c64..178a2b0 100644
--- a/printed/pcb_mount.scad
+++ b/printed/pcb_mount.scad
@@ -103,10 +103,9 @@ module pcb_mount_assembly(pcb, thickness, height = 5) { //! A PCB mount assembly
 
     stl_colour(pp1_colour) pcb_mount(pcb, washers = false);
 
-    washer = screw_washer(screw);
     nut = screw_nut(screw);
     t = pcb_thickness(pcb);
-    screw_length = screw_longer_than(height + t + washer_thickness + thickness + washer_thickness(washer) + nut_thickness(nut, true));
+    screw_length = screw_length(screw, height + t + washer_thickness + thickness, 1, nyloc = true);
 
     pcb_mount_screw_positions(pcb) {
         translate_z(height + t) {
diff --git a/printed/printed_box.scad b/printed/printed_box.scad
index bf196a7..7ee0167 100644
--- a/printed/printed_box.scad
+++ b/printed/printed_box.scad
@@ -65,10 +65,8 @@ function pbox_insert(type) = screw_insert(pbox_screw(type)); //! The insert for
 function pbox_washer(type) = screw_washer(pbox_screw(type)); //! The washer for the base screws
 
 function pbox_screw_length(type, panel_thickness = 0) =  //! Length of the base screw
-    let(foot = pbox_foot(type))
-        screw_shorter_than(pbox_base(type) + washer_thickness(pbox_washer(type))
-                            + insert_length(pbox_insert(type))
-                            + (foot ? foot_thickness(foot) : panel_thickness));
+    let(foot = pbox_foot(type), screw = pbox_screw(type))
+        screw_length(screw, pbox_base(type) + (foot ? foot_thickness(foot) : panel_thickness), 1, true);
 
 function pbox_mid_offset(type) = pbox_ridges(type).y + pbox_wall(type) / 2; // Offset to wall midpoint
 
diff --git a/printed/psu_shroud.scad b/printed/psu_shroud.scad
index 23732f7..8343fc9 100644
--- a/printed/psu_shroud.scad
+++ b/printed/psu_shroud.scad
@@ -156,8 +156,7 @@ assembly(str("PSU_shroud_", name)) {
 
 module psu_shroud_fastened_assembly(type, cable_d, thickness, name, cables = 1) //! Assembly with screws in place
 {
-    washer = screw_washer(screw);
-    screw_length = screw_shorter_than(2 * washer_thickness(washer) + thickness + insert_length(insert) + counter_bore);
+    screw_length = screw_length(screw,thickness + counter_bore, 2, true);
 
     psu_shroud_assembly(type, cable_d, name, cables);
 
diff --git a/printed/ribbon_clamp.scad b/printed/ribbon_clamp.scad
index 19ae83c..6bbd41b 100644
--- a/printed/ribbon_clamp.scad
+++ b/printed/ribbon_clamp.scad
@@ -101,8 +101,7 @@ module ribbon_clamp_fastened_assembly(ways, thickness, screw = screw) { //! Clam
 
     vitamin(str(": Tape self amalgamating silicone ",tape_l," x 25mm"));
 
-    washer = screw_washer(screw);
-    screw_length = screw_shorter_than(2 * washer_thickness(washer) + thickness + ribbon_clamp_screw_depth(screw));
+    screw_length = screw_length(screw, thickness + ribbon_clamp_screw_depth(screw), 2);
 
     ribbon_clamp_assembly(ways, screw);
 
diff --git a/printed/socket_box.scad b/printed/socket_box.scad
index 72e785c..e5f0216 100644
--- a/printed/socket_box.scad
+++ b/printed/socket_box.scad
@@ -105,8 +105,7 @@ module socket_box_MKLOGIC_assembly() socket_box_assembly(MKLOGIC);
 
 module socket_box_fastened_assembly(type, thickness) { //! The socket and backbox on each side of the specified panel thickness
     screw = mains_socket_screw(type);
-    insert = screw_insert(screw);
-    screw_length = screw_longer_than(mains_socket_height(type) + thickness + insert_length(insert));
+    screw_length = screw_length(screw, mains_socket_height(type) + thickness, 0, true, longer = true);
 
     explode(-50)
         translate_z(-height - thickness)
diff --git a/printed/ssr_shroud.scad b/printed/ssr_shroud.scad
index ac9132f..5fbb335 100644
--- a/printed/ssr_shroud.scad
+++ b/printed/ssr_shroud.scad
@@ -119,8 +119,7 @@ assembly(str("SSR_shroud_", name)) {
 
 module ssr_shroud_fastened_assembly(type, cable_d, thickness, name) //! Assembly with screws in place
 {
-    washer = screw_washer(screw);
-    screw_length = screw_shorter_than(2 * washer_thickness(washer) + thickness + insert_length(insert) + counter_bore);
+    screw_length = screw_length(screw, thickness + counter_bore, 2, true);
 
     ssr_shroud_assembly(type, cable_d, name);
 
diff --git a/printed/strap_handle.scad b/printed/strap_handle.scad
index 639cab3..e53e3f7 100644
--- a/printed/strap_handle.scad
+++ b/printed/strap_handle.scad
@@ -172,11 +172,9 @@ assembly("strap_end") {
 
 module strap_assembly(length, type = strap) { //! Assembly with screws in place
     screw = strap_screw(type);
-    washer = screw_washer(screw);
-    penny = penny_washer(washer);
-    insert = strap_insert(type);
+    penny = penny_washer(screw_washer(screw));
 
-    screw_length = screw_shorter_than(washer_thickness(washer) + washer_thickness(penny) + insert_length(insert) + panel_clearance + counterbore);
+    screw_length = screw_length(screw, washer_thickness(penny) + panel_clearance + counterbore, 1, true);
 
     stl_colour(pp4_colour) strap(length, type);
 
diff --git a/readme.md b/readme.md
index a65fa72..96b460b 100644
--- a/readme.md
+++ b/readme.md
@@ -2902,10 +2902,11 @@ For an explanation of `screw_polysink()` see <https://hydraraptor.blogspot.com/2
 |:--- |:--- |
 | `screw_boss_diameter(type)` | Boss big enough for nut trap and washer |
 | `screw_head_depth(type, d = 0)` | How far a counter sink head will go into a straight hole diameter d |
-| `screw_longer_than(x)` | Returns shortest screw length longer or equal to x |
+| `screw_length(screw, thickness, washers, insert = false, nyloc = false, nut = false, longer = false)` | Returns the length of the longest or shortest screw that will got through `thickness` and `washers` and possibly an `insert`, `nut` or `nyloc` |
+| `screw_longer_than(x)` | Returns the length of the shortest screw length longer or equal to x |
 | `screw_nut_radius(type)` | Radius of matching nut |
 | `screw_polysink_r(type, z)` | Countersink hole profile corrected for rounded staircase extrusions. |
-| `screw_shorter_than(x)` | Returns longest screw length shorter than or equal to x |
+| `screw_shorter_than(x)` | Returns the length of the longest screw shorter than or equal to x |
 
 ### Modules
 | Module | Description |
diff --git a/tests/BOM.scad b/tests/BOM.scad
index 99335be..8680dc1 100644
--- a/tests/BOM.scad
+++ b/tests/BOM.scad
@@ -30,7 +30,6 @@ sheet = PMMA3;
 height = 10;
 
 insert = screw_insert(screw);
-washer = screw_washer(screw);
 
 module widget(thickness) {
     vitamin(str("widget(", thickness, "): Rivit like thing for ", thickness, "mm sheets"));
@@ -92,7 +91,7 @@ assembly("wigdit") {
 
     translate_z(height) {
         translate_z(sheet_thickness(sheet))
-            screw_and_washer(screw, screw_longer_than(sheet_thickness(sheet) + 2 * washer_thickness(washer) + 3), true);
+            screw_and_washer(screw, screw_length(screw, sheet_thickness(sheet) + 3, 2, longer = true), true);
 
         explode(5)
             translate_z(sheet_thickness(sheet) / 2 + eps)
diff --git a/tests/blowers.scad b/tests/blowers.scad
index 1dcb243..6ae503f 100644
--- a/tests/blowers.scad
+++ b/tests/blowers.scad
@@ -24,16 +24,13 @@ include <../vitamins/blowers.scad>
 module blowers()
     layout([for(b = blowers) blower_width(b)], 10, true) let(b = blowers[$i]){
         screw = blower_screw(b);
-        washer = screw_washer(screw);
         h = blower_lug(b);
 
         blower(b);
 
         blower_hole_positions(b)
             translate_z(h)
-                screw_and_washer(screw, screw_longer_than(h + washer_thickness(washer) + 5));
-
-
+                screw_and_washer(screw, screw_length(screw, h + 5, 1, longer = true));
     }
 
 if($preview)
diff --git a/vitamins/fan.scad b/vitamins/fan.scad
index a8fa237..57f970e 100644
--- a/vitamins/fan.scad
+++ b/vitamins/fan.scad
@@ -151,10 +151,8 @@ function fan_screw_depth(type, full_depth = false) = fan_boss_d(type) || full_de
 
 function fan_screw_length(type, thickness, full_depth = false) =
     let(depth = fan_screw_depth(type, full_depth),
-        washers = depth == fan_depth(type) ? 2 : 1,
-        washer = screw_washer(fan_screw(type)),
-        nut = screw_nut(fan_screw(type)))
-            screw_longer_than(thickness + depth + washer_thickness(washer) * washers + nut_thickness(nut, true)); //! Screw length required
+        washers = depth == fan_depth(type) ? 2 : 1)
+            screw_length(fan_screw(type), thickness + depth, washers, nyloc = true); //! Screw length required
 
 module fan_assembly(type, thickness, include_fan = true, screw = false, full_depth = false) { //! Fan with its fasteners
     translate_z(-fan_depth(type) / 2) {
diff --git a/vitamins/iec.scad b/vitamins/iec.scad
index ddebe90..7dd9698 100644
--- a/vitamins/iec.scad
+++ b/vitamins/iec.scad
@@ -247,10 +247,7 @@ module iec_inserts(type) {              //! Place the inserts
 
 module iec_assembly(type, thickness) {  //! Assembly with fasteners given panel thickness
     screw = iec_screw(type);
-    washer = screw_washer(screw);
-    nut = screw_nut(screw);
-    insert = screw_insert(screw);
-    screw_length = thickness ? screw_longer_than(iec_flange_t(type) + thickness + washer_thickness(washer) + nut_thickness(nut, true))
+    screw_length = thickness ? screw_length(screw, iec_flange_t(type) + thickness, 1, nyloc = true)
                              : insert_screw_length;
 
     iec(type);
@@ -262,6 +259,6 @@ module iec_assembly(type, thickness) {  //! Assembly with fasteners given panel
         if(thickness)
             translate_z(-thickness)
                 vflip()
-                    nut_and_washer(nut, true);
+                    nut_and_washer(screw_nut(screw), true);
     }
 }
diff --git a/vitamins/module.scad b/vitamins/module.scad
index 511ff50..7afcb1b 100644
--- a/vitamins/module.scad
+++ b/vitamins/module.scad
@@ -129,15 +129,13 @@ module mod_screw_positions(type) //! Position children at the screw positions
 
 module module_assembly(type, thickness) { //! Module with its fasteners in place
     screw = mod_screw(type);
-    washer = screw_washer(screw);
-    nut = screw_nut(screw);
-    screw_length = screw_longer_than(thickness + mod_screw_z(type) + 2 * washer_thickness(washer) + nut_thickness(nut, true));
+    screw_length = screw_length(screw, thickness + mod_screw_z(type), 2, nyloc = true);
 
     mod(type);
 
     mod_screw_positions(type) {
         translate_z(mod_screw_z(type))
-            nut_and_washer(nut, true);
+            nut_and_washer(screw_nut(screw), true);
 
         translate_z(-thickness)
             vflip()
diff --git a/vitamins/pcb.scad b/vitamins/pcb.scad
index 8b0b150..21d80b4 100644
--- a/vitamins/pcb.scad
+++ b/vitamins/pcb.scad
@@ -1121,9 +1121,7 @@ module pcb_assembly(type, height, thickness) { //! Draw PCB assembly with spaces
 
     screw = pcb_screw(type);
     if(!is_undef(screw)) {
-        washer = screw_washer(screw);
-        nut = screw_nut(screw);
-        screw_length = screw_longer_than(height + thickness + pcb_thickness(type) + washer_thickness(washer) + nut_thickness(nut, true));
+        screw_length = screw_length(screw, height + thickness + pcb_thickness(type), 1, nyloc = true);
 
         taper = screw_smaller_than(pcb_hole_d(type)) > 2 * screw_radius(screw); // Arduino?
         pcb_screw_positions(type) {
@@ -1138,7 +1136,7 @@ module pcb_assembly(type, height, thickness) { //! Draw PCB assembly with spaces
 
             translate_z(-thickness)
                 vflip()
-                    nut_and_washer(nut, true);
+                    nut_and_washer(screw_nut(screw), true);
         }
     }
 }
diff --git a/vitamins/ring_terminal.scad b/vitamins/ring_terminal.scad
index f952595..9c71408 100644
--- a/vitamins/ring_terminal.scad
+++ b/vitamins/ring_terminal.scad
@@ -128,7 +128,7 @@ module ring_terminal_assembly(type, thickness, top = false) { //! Earthing assem
     screw = ringterm_screw(type);
     washer = screw_washer(screw);
     nut = screw_nut(screw);
-    screw_length = screw_longer_than(thickness + 2 * washer_thickness(washer) + nut_thickness(nut, true) + ringterm_thickness(type));
+    screw_length = screw_length(screw, thickness + ringterm_thickness(type), 2, nyloc = true);
 
     explode(10, true) star_washer(washer)
         if(top)
diff --git a/vitamins/screw.scad b/vitamins/screw.scad
index 98d9686..8cb9dba 100644
--- a/vitamins/screw.scad
+++ b/vitamins/screw.scad
@@ -48,7 +48,7 @@ function screw_head_depth(type, d = 0) =             //! How far a counter sink
         ? 0
         : let(r = screw_radius(type)) screw_head_radius(type) - max(r, d / 2) + r / 5;
 
-function screw_longer_than(x) = x <=  5 ?  5 : //! Returns shortest screw length longer or equal to x
+function screw_longer_than(x) = x <=  5 ?  5 : //! Returns the length of the shortest screw length longer or equal to x
                                 x <=  6 ?  6 :
                                 x <=  8 ?  8 :
                                 x <= 10 ? 10 :
@@ -56,7 +56,7 @@ function screw_longer_than(x) = x <=  5 ?  5 : //! Returns shortest screw length
                                 x <= 16 ? 16 :
                                 ceil(x / 5) * 5;
 
-function screw_shorter_than(x) = x >= 20 ? floor(x / 5) * 5 : //! Returns longest screw length shorter than or equal to x
+function screw_shorter_than(x) = x >= 20 ? floor(x / 5) * 5 : //! Returns the length of the longest screw shorter than or equal to x
                                  x >= 16 ? 16 :
                                  x >= 12 ? 12 :
                                  x >= 10 ? 10 :
@@ -64,6 +64,14 @@ function screw_shorter_than(x) = x >= 20 ? floor(x / 5) * 5 : //! Returns longes
                                  x >=  6 ?  6 :
                                  5;
 
+function screw_length(screw, thickness, washers, insert = false, nyloc = false, nut = false, longer = false) = //! Returns the length of the longest or shortest screw that will got through `thickness` and `washers` and possibly an `insert`, `nut` or `nyloc`
+    let(washer = washers ? washers * washer_thickness(screw_washer(screw)) : 0,
+        insert = insert ? insert_length(screw_insert(screw)) : 0,
+        nut = nut || nyloc ? nut_thickness(screw_nut(screw), nyloc)  : 0,
+        total = thickness + washer + insert + nut
+       )
+        longer || nut || nyloc ? screw_longer_than(total) : screw_shorter_than(total);
+
 function screw_smaller_than(d) = d >= 2.5 && d < 3 ? 2.5 : floor(d); // Largest diameter screw less than or equal to specified diameter
 
 function screw_insert(screw, i = 0) = let(d = screw_radius(screw) * 2)
diff --git a/vitamins/ssr.scad b/vitamins/ssr.scad
index 7ab86f4..0d19274 100644
--- a/vitamins/ssr.scad
+++ b/vitamins/ssr.scad
@@ -71,15 +71,13 @@ use <nut.scad>
 use <washer.scad>
 
 module ssr_assembly(type, screw, thickness) { //! Assembly with fasteners in place
-    nut = screw_nut(screw);
-    washer = screw_washer(screw);
-    screw_length = screw_longer_than(2 * washer_thickness(washer) + thickness + ssr_base_t(type) + nut_thickness(nut, true));
+    screw_length = screw_length(screw, thickness + ssr_base_t(type), 2, nyloc = true);
 
     ssr(type);
 
     ssr_hole_positions(type) {
         translate_z(ssr_base_t(type))
-            nut_and_washer(nut, true);
+            nut_and_washer(screw_nut(screw), true);
 
         translate_z(-thickness)
             vflip()
diff --git a/vitamins/veroboard.scad b/vitamins/veroboard.scad
index 7cbd720..41c7e6f 100644
--- a/vitamins/veroboard.scad
+++ b/vitamins/veroboard.scad
@@ -146,9 +146,8 @@ module vero_cutouts(type, angle = undef) vero_components(type, true, angle); //!
 module veroboard_assembly(type, height, thickness, flip = false) //! Draw the assembly with components and fasteners in place
 assembly(vero_assembly(type)) {
     screw = vero_screw(type);
-    washer = screw_washer(screw);
     nut = screw_nut(screw);
-    screw_length = screw_longer_than(height + thickness + vero_thickness(type) + 2 * washer_thickness(washer) + nut_thickness(nut, true));
+    screw_length = screw_length(screw, height + thickness + vero_thickness(type), 2, nyloc = true);
 
     translate_z(height) {
         veroboard(type);