Hi! My name is Matthew Christian from Tampa, Florida and on behalf of Expert Village, I would like to talk to you about the proper use of a hammerdrill. Once you've determined the size drill bit that you need, you can go ahead and install your drill bit. This particular drill requires a key for the chuck. What we will do is open the chuck enough to get our drill bit in. Once you have the chuck opened enough, you insert the drill bit. Also being sure to insert the drill bit not necessarily all the way but close to it. You don't want the drill bit only in slightly but you want the drill bit to get enough in there so that chuck has something to hold on to. So we install the drill bit and we are going to tighten the chuck and give it a good snug tightened but also turn the chuck over to the next hole and give it another snug tightened and then once again, by doing do this will ensure that you have the chuck tightened evenly and securely on your drill bit. Now the chuck that we just used, had a key. Some models have a keyless chuck and you simply the hold the chuck as you tighten or loosen the chuck and it doesn't require a key. Both are just as good. Just some models have a keyless chuck and others use a key.