The other end of the supporting rope is connected to a counterweight in the attic space above, so relatively little force is needed to move the cover.
Due to friction I have made the counterweight sufficient only to stop the covers falling - a light downward pressure will bring them gently down. More force is need to raise them and this is provided by 'pull-up' lines, one of which is seen on the right here; pulling down on this pulls up in the centre of the box, next to the main support ropes, and so ensures the cover rises squarely.
The box is a touch larger than the baseboards so it drops 1/2" down the sides to rest on wood blocks.