Most crosscut sled designs have wood or plastic guards to act as a barrier against the blade protruding through the rear fence and causing injury. While these barriers are certainly necessary, they do not stop the forward travel of the sled, which can lead to a false sense of security.
So I’ve added an “L”-shaped “tail hook” that automatically flips up and engages the infeed/front of the saw table each time I push the sled forward for a cut. My tail hook’s 12″ length and pivot screw location stop the sled’s forward travel before the saw blade can reach the back end of the rear guard. I made it from 1/4″-thick scrap plywood.