To provide for a more secure hold-down for a metal rule, pin it down with half your finger, using the other half to press down on the workpiece.
When drawing or knifing mark-up lines, a slippery metal rule can shift off of its mark. Instead of pressing down on it with the whole pads of your fingers, use just half the pad of your thumb and middle finger. Press the other half against the workpiece. It pins the rule down more securely.
