Reasons interface is a virtual hardware rack of synthesizers, samplers, mixers and effects. When you create a "Subtractor" synthesizer, there are 4 screws as part of the visual device, if you click and hold on one of the screws, then move the mouse up, you will twist the screw out of its hole.

Click and hold again in the empty space, move the mouse down and it will replace the crew and you may tighten it down all the way.

The only thing I find that it deos is makes the device immovable. The Subtractor synthesizer is the only device I could do this on, but maybe there are more eggs in Reason.