diff --git a/kblock_ext/kblock_ext.scad b/kblock_ext/kblock_ext.scad
new file mode 100644
index 0000000..9515856
--- /dev/null
+++ b/kblock_ext/kblock_ext.scad
@@ -0,0 +1,48 @@
+h=5;
+r0=3;
+$fn=50;
+l=60;
+w=30;
+magnet_play=0.5;
+magnet_l=19.5+magnet_play;
+magnet_w=5.8+magnet_play;
+magnet_h=2.7+magnet_play;
+magnet_hole_h=0.8*h;
+screw_play=0.5;
+screw_head_r=6.8/2 + screw_play;
+screw_thread_r=3.5/2 + screw_play;
+screw_head_h=2.5 + screw_play;
+color("green", 1.0) {
+  difference()
+  {
+    translate([r0, r0, 0])
+    hull() {
+      for (x=[0:1:1]) {
+        for (y=[0:1:1]) {
+        translate([(l-2*r0)*x, (w-2*r0)*y, 0])
+          cylinder(h, r=r0, center=true);
+        }
+      }
+    }
+    union() {
+      translate([0.1*l, w/2, 0])
+      cylinder(h+0.001, r=screw_thread_r, center=true);
+      // For screw head
+      translate([0.1*l, w/2, h/2-screw_head_h/2+0.001])
+      cylinder(screw_head_h, r1=screw_thread_r, r2=screw_head_r, center=true);
+      translate([0.9*l, w/2, 0])
+      cylinder(h+0.001, r=screw_thread_r, center=true);
+      // For screw head
+      translate([0.9*l, w/2, h/2-screw_head_h/2+0.001])
+      cylinder(screw_head_h, r1=screw_thread_r, r2=screw_head_r, center=true);
+    }
+    translate([l/2, 0, 0])
+    union() {
+      for (x=[-1:1:1]) {
+        translate([x*2.0*magnet_w, w/2, -h/2+magnet_hole_h/2-0.001])
+        rotate([0, 0, 90])
+        cube([magnet_l, magnet_w, magnet_hole_h], center=true);
+      }
+    }
+  }
+}