You find yourself in the side position unable to gain the mount.

Your opponent crosses his ankles and raises his knees in order to block you gaining the mount. Grab the top of his top foot.

Reach under his bottom calf with your other hand and grab the top of his top foot. Pull his foot down as you raise your forearms. This should be extremely painful on his achiles tendon.

More than likely, he will roll out of it to relieve pain. Follow him and attempt to apply pressure constantly.

Step up and hook his crossed ankles in your hip as you lean forward, applying pressure to his knees and imobilizing him in a superior position.