difference() {
    cube([115,60,15]);
    union() {
        translate([10,30,-1]) cylinder(r=5, h=17);
        translate([-1,25,-1]) cube([11,10,17]);
        translate([105,30,-1]) cylinder(r=5, h=17);
        translate([105,25,-1]) cube([11,10,17]);
        translate([57.5,30,-1]) cylinder(r=9, h=17);
    }
}
translate([25,0,15]) cube([7,60,7]);
translate([83,0,15]) cube([7,60,7]);
translate([25,0,22]) cube([15,60,8]);
translate([75,0,22]) cube([15,60,8]);
polyhedron(
    points=[ [90,10,15],[115,10,15],[90,10,30],
               [90,15,15],[115,15,15],[90,15,30] ],
    triangles=[ [0,1,2],[0,3,5,2],[3,4,5],[0,1,4,3],[1,4,5,2] ]);
polyhedron(
    points=[ [90,45,15],[115,45,15],[90,45,30],
               [90,50,15],[115,50,15],[90,50,30] ],
    triangles=[ [0,1,2],[0,3,5,2],[3,4,5],[0,1,4,3],[1,4,5,2] ]);
polyhedron(
    points=[ [0,10,15],[25,10,15],[25,10,30],
               [0,15,15],[25,15,15],[25,15,30] ],
    triangles=[ [0,1,2],[0,3,5,2],[3,4,5],[0,1,4,3],[1,4,5,2] ]);
polyhedron(
    points=[ [0,45,15],[25,45,15],[25,45,30],
               [0,50,15],[25,50,15],[25,50,30] ],
    triangles=[ [0,1,2],[0,3,5,2],[3,4,5],[0,1,4,3],[1,4,5,2] ]);