Self-centering. A self-centering chuck, also known as a scroll chuck, uses dogs (usually called jaws), interconnected via a scroll gear (scroll plate), to hold onto a tool or workpiece. Elf centering chucks can be fitted with 2 jaws, 3 jaws, 4 jaws, or 6 jaws, dependent on the needs of the operator and the work being done. Elf-centering three-jaw chuck and key with one jaw removed and inverted showing the teeth that engage in the scroll plate. The scroll plate is rotated within the chuck body by the key, the scroll engages the teeth on the underside of the jaws which moves the three jaws in unison, to tighten or release the workpiece.