def stack_this_under_that(this, that):
    if isinstance(this, cq.occ_impl.shapes.Compound):
        this_top = this.BoundingBox().zmax
    else:
        this_top = this.bounding_box().max.Z

    if that == 'Z':
        that_bottom = 0
    else:
        if isinstance(that, cq.occ_impl.shapes.Compound):
            that_bottom = that.BoundingBox().zmin
        else:
            that_bottom = that.bounding_box().min.Z

    move_z = that_bottom - this_top

    this.move(bd.Location((0,0,move_z),(0,0,0)))

    return

def stack_this_on_that(this, that):
    if isinstance(this, cq.occ_impl.shapes.Compound):
        this_bottom = this.BoundingBox().zmin
    else:
        this_bottom = this.bounding_box().min.Z

    if that == 'Z':
        that_top = 0
    else:
        if isinstance(that, cq.occ_impl.shapes.Compound):
            that_top = that.BoundingBox().zmax
        else:
            that_top = that.bounding_box().max.Z

    move_z = that_top - this_bottom

    this.move(bd.Location((0,0,move_z),(0,0,0)))
    return