fn box = (h, l, w) => {
 const myBox = startSketchOn(XY)
    |> startProfile(at = [0,0])
    |> line(end = [0, l])
    |> line(end = [w, 0])
    |> line(end = [0, -l])
    |> close()
    |> extrude(length = h)

  return myBox
}

const fnBox = box(3, 6, 10)