diff --git a/README.md b/README.md
index 76a7536..450c08e 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,12 @@
 # Senkung
 
-Senkung für Senkkopfschrauben als Modul
\ No newline at end of file
+Senkung für Senkkopfschrauben als Modul
+
+usage:
+
+use <countersunk_hole.scad>
+
+difference(){
+    cube([8,8,3.4]);
+    translate([4, 4, 2.5]) countersunk_hole(2.5);
+}
diff --git a/contersunk_hole.scad b/contersunk_hole.scad
new file mode 100644
index 0000000..1c95e15
--- /dev/null
+++ b/contersunk_hole.scad
@@ -0,0 +1,14 @@
+/ M3
+body_diameter=3.2; // screw body
+head_diameter=6.4; // screw head max
+depth=1; // head-rim clearance
+detail=50;
+
+module countersunk_hole(hole_depth) {
+    rotate([0, 180, 0]) {
+        cylinder(h=depth, d1=head_diameter, d2=body_diameter, $fn=detail);
+        cylinder(h=hole_depth, d=body_diameter, $fn=detail);
+        translate([0, 0, -(depth)])
+        cylinder(h=depth, d=head_diameter, $fn=detail);
+    }
+}