+module Hook(){
+ rotate([90,0,0]){
+ difference(){
+ union(){
+ linear_extrude(height=back_th)
+ BackPlan();
+ linear_extrude(height=back_th+gap_th+front_th)
+ MidPlan();
+ translate([0,0, back_th+gap_th])
+ linear_extrude(height=front_th) FrontPlan();
+ }
+ }
+ }
+}
+