The Drill-powered shear will cut straight or slight curves, as well as making 90 degree corners. It requires a half inch pilot hole to get started and is easily attached to your cordless or electric drill (not included).
The adjustable circular hole cutter is the easiest to use. It requires a cordless or electric drill (not included), and will drill its own 1/8 inch center hole. The sliding/locking center pivot pin has a built in scale to cut precise holes from 2 to 12 inches in diameter.