Abstract: A sliding door system includes a pair of sliding doors which ride on J-shaped tracks. A stopper, formed of a block of deformable material, has a J-shaped channel which generally matches the contour of the J-shaped tracks. One presses the stopper onto the inner track, at one of the ends of the track. When the inner door is moved to an extreme position, it abuts the stopper, and cannot reach the door frame. Thus, there is a recess between the door frame and the inner door. The recess makes it easy to move the inner door when it is desired to close the closet. Also, the stopper prevents an indentation, formed on the inner door, from being obscured by the outer door, when the inner door is opened. The stopper is made of an elastomeric material so that it can be easily inserted onto the track, without special tools. Thus, the stopper can be easily retrofitted onto existing tracks for sliding door systems, without modifying such systems.