If you don't know what the jaw clamp is for then you probably don't have a GoPro yet. It isn't a big deal, we carry those to. The moment you get one of these cameras you tend to look for any and every place you can put it. The jaw clamp is a GoPro enabler. It allows you to clip your camera onto that nearby fence so you can get a shot of a peloton passing by. It actually clamps on to just about anything that is nearby and adjusts quickly so you can get the shot. Let's be honest, the best shots that a GoPro's gets are typically places that a cameraman shouldn't stand, so this allows you to get that shot without putting yourself in harms way.
The Jaw clamp is able to attach firmly to irregular objects that range from .25" to 2" thick. It has two options, the camera can either attach directly to the clamp or it is able to attach to the flexible arm that attaches to the clamp.