bascially there r 3 diffrent type of gravel pads, the first tupe of pad u will encounter, and most likely use is the leather bag..... your first step is to hit these wearing bag mits as im sure you do..... second hit it with hand wraps, then bare nuckle... now move onto the second bag, its a thin bag about 3' thick, u put it on the all, its full of sand and is made of canvas .. this will tuffen your hand even more, next is a tray full of sand, when u r tuff enuff ... i.e the skin on your hand, you should hit the sand with a good deal of power and develop furthermore .... its to stop your hands splitting when you hit someone in the face... aslo can b used for elbows, shins etc.........
If u want to strengthen, i highley recommend an eagal catcher .. it will develop yoru hands well . start with push ups on hands, then nuckles, then all 5 fingers, then 4, then 3, then 2, then 1, untill finally that last one is your thumb....... these routines will greatly improve your physical ability at trapping.