diff --git a/pen_plotter.scad b/pen_plotter.scad
index 881f6be..7782a9a 100644
--- a/pen_plotter.scad
+++ b/pen_plotter.scad
@@ -44,9 +44,23 @@ module linear_shafts() {
     cylinder(110, 3.5, 3.5);
 }
 
-module sled() {
-  translate([150, 130, 100])
-    cube([30, 20, 50]);
+module sled(width = 20) {
+  translate([150, 130, 100]) {
+    difference() {
+      cube([30, width, 50]);
+      union() {
+	translate([-30, width, -40])
+	  rotate([90, 0, 0])
+	  cylinder(width, 60, 60);
+	translate([10, width, 40])
+	  rotate([90, 0, 0])
+	  cylinder(width, 4, 4);
+	translate([20, width, 10])
+	  rotate([90, 0, 0])
+	  cylinder(width, 4, 4);
+      }
+    }
+  }
 }
 
 color([0,0,0]) floor();