A grinder, also known as a crusher or crumbler , is intended for grinding cannabis or other herbs. This leaves you with a crumbled remnant of the originally larger parts, so you can easily distribute the crumbled remains. Especially when rolling a joint, crumbling the weed is a requirement so that it can be properly distributed over the entire (long) paper. The grinder, or crumbler, makes crumbling weed easier, faster and better than doing it by hand.