A drill chuck is a special clamp that is used for holding the rotating bit; because of this, sometimes it is called the bit holder. In drills, chucks usually have several jaws to secure the bit. In some models, you need a chuck key to loosen or tighten the chuck, these are called keyed chucks. In other models however, you are needless of a key and can easily loosen or tighten the chuck by your hands, these are called keyless chucks. Almost all the cordless drills are equipped with keyless chucks. Although working with keyless chucks are more preferred because of their easiness, keyed chucks provide more security especially for heavier applications.