difference(){
        difference(){
                union(){
                        difference(){
                                cylinder(h=20,r=14,$fn=100);
                                cylinder(h=3*20,r=10,center=true,$fn=100);
                        }
                        difference(){
                                translate([2+1,0,10]){cube([4,50,20],center=true);}
                                cylinder(h=3*20,r=10,center=true,$fn=100);
                        }
                }
                translate([-15+1,0,10]){cube(30,center=true);}
        }
        union(){
                translate([0,19.5,10]){rotate([0,90,0]){cylinder(h=10,r=3,$fn=100);}}
                translate([0,-19.5,10]){rotate([0,90,0]){cylinder(h=10,r=3,$fn=100);}}
        }
}