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

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

part002 = startSketchOn(part001, "END")
  |> startProfileAt([0, 0], %)
  |> line(end = [0, 10])
  |> line(end = [10, 0])
  |> line(end = [0, -10])
  |> close(%)
  |> extrude(length = 5)