Wikibooks: OpenSCAD User Manual
rotate_extrude(convexity=10,$fn=100)
translate([2,0,0])
circle(r=1,$fn=100);
difference() {
cube(size =[12,21,2],center=true);
translate ([0,0,1])
cube(size =[10,21,2],center=true);
}
union(){
translate ([4.5,9,-3.5])
cylinder(h=5, r=1, center=true, $fn=100);
translate ([-4.5,9,-3.5])
cylinder(h=5, r=1, center=true, $fn=100);
translate ([-5.5,9,-2])
rotate ([90,0,90]) cylinder (r=1, h=11,$fn=100);
}
union(){
translate ([4.5,-9,-3.5])
cylinder(h=5, r=1, center=true, $fn=100);
translate ([-4.5,-9,-3.5])
cylinder(h=5, r=1, center=true, $fn=100);
translate ([-5.5,-9,-2])
rotate ([90,0,90]) cylinder (r=1, h=11,$fn=100);