Side Rails are 2″ inches wide, 3/4″ deep. The bottom bar moves vertically inside the channel. There is a 1/4″ gap from the fabric to the Side Rail. This is done intentionally so that the wind cannot blow the shade out of the center of them. The Side Rail acts as a guide that helps prevent the shade bottom from blowing out or twisting in the wind. They are a good way to keep the bottom of motorized shades locked in place if you do not use a cable system.