Drill bit shank The name comes from the German "Stecken – Drehen – Sichern" (Insert – Twist – Secure). In German-speaking countries the back-formation "Spannen durch System" (Clamping System) is used, though Bosch uses "Special Direct System" for international purposes. The triangle shank is almost always made by machining three flats on round bar stock. It is intended as a minor modification of a straight shank, still allowing it to be held in a 3-jaw drill chuck, but allowing higher torque transmission and limited slipping. The Morse taper twist drill bits pictured right are used in metalworking. The full range of tapers is
Tightening key Tightening key A corner key or tightening key is a small wedge or block of board, timber or plastic, inserted into the slotted inside corners of a canvas stretcher frame to prevent or adjust sagging. The piece is tapped in to expand the stretcher bars slightly, tensioning the canvas. The keys can be used to re-tighten the canvas as it relaxes naturally over time. Tightening keys are commonly made in plastic or wood, and are commonly known as corner keys or corner wedges. Corner keys or wedges come in various forms. Most are available for a single size stretcher bar,