A drill uses either a keyed or a keyless chuck. The chuck is the portion of the drill on the end that clamps onto and holds the bit. Some users prefer drills with keyed chucks, because the jaws of this type of chuck normally grip the bit tighter than a keyless model. You lock the chuck when you install a bit into the drill, and unlock it when you want to remove the bit and replace it with another one.
Unplug the drill from an electrical outlet, if it is corded and plugged in. Grip the drill with one hand.
Grip the chuck on the nose of the drill and push it in, if necessary. For a keyless chuck, twist the chuck counterclockwise to open the jaws.
Locate a small hole on the side of the drill chuck in a keyed chuck. The chuck may have more than one hole on it. Insert the end of the t-shaped chuck key into one of the holes, and turn the key counterclockwise to unlock and open the jaws.