A works-like rig is a box with the real parts inside: the heater, the LEDs, the battery, the motor (sample note).
It does not look like the product and it is not meant to. Its job is to prove that the product works before anyone pays for tools: that the kettle boils in time, that the light lasts a week, that the lamp head stays cool.
Every rig I build gets a tag with the question it answers and a page of test figures. When the figures are in, it goes on the shelf.