This solution is superior to Catalina's removable machine screw stop in that it is harder to lose. When it's necessary to remove the sail slides, just loosen the knurled nut by hand, slide the stop down past the entrance slot, and retighten. There's little chance of losing it. No need to find a pocket to put a machine screw in.

Includes large knurled nut. Plate which inserts into the track is 3/4" wide X 1" high X 1/8" thick.

All of the above masts have a sail track approximately 0.78" wide inside. In order to insert the stop into the track, the sail track must have been relieved to both port and starboard at the factory in order for the entrance slot to be wide enough to accept this sail track stop. On a few boats, for reasons unknown to us, Catalina only relieved one side of the mast track. In those rare cases, this track stop will not work without modification to its width.