fn cube(pos, scale) {
  sg = startSketchOn(XY)
    |> startProfile(at = pos)
    |> line(end = [0, scale])
    |> line(end = [scale, 0])
    |> line(end = [0, -scale])

  return sg
}
part001 = cube(pos = [0,0], scale = 20)
    |> close()
    |> extrude(length = 20)

part002 = startSketchOn(part001, face = "start")
  |> startProfile(at = [0, 0])
  |> line(end = [0, 10])
  |> line(end = [10, 0])
  |> line(end = [0, -10])
  |> close()
  |> extrude(length = 5)
