cube([20,83,22]);
translate([-15,0]) cube([15,83,30]);
translate([20,0,0]) cube([15,83,72]);
polyhedron(
  points=[[0,0,30],[-15,0,30],[0,83,30],[-15,83,30],[0,0,50],[-15,0,50]],
  triangles=[[0,2,4],[1,3,5],[0,1,3,2],[0,1,5,4],[2,3,5,4]]);