l=65; w=16; h=4; hole=8.5; difference(){ union(){ translate([(l-w)/2,0,0]) cylinder(r=w/2,h=h, $fn=100, center=true); translate([-(l-w)/2,0,0]) cylinder(r=w/2,h=h, $fn=100, center=true); translate([0,0,0]) #cube([l-(w),w,h], center=true); } translate([(l-w)/2,0,0]) cylinder(r=hole/2,h=h, $fn=100, center=true); translate([-(l-w)/2,0,0]) cylinder(r=hole/2,h=h, $fn=100, center=true); translate([((l-w)-hole)/2,0,0]) cylinder(r=hole/2,h=h, $fn=100, center=true); translate([((l-w)-(hole/2))/2,0,0]) cube([hole/2,hole,h], center=true); translate([-((l-w)-hole)/2,0,0]) cylinder(r=hole/2,h=h, $fn=100, center=true); translate([-((l-w)-(hole/2))/2,0,0]) cube([hole/2,hole,h], center=true); }