These clamps are ideal for repairing cracks in stringed instrument tops and backs. They have a large array of applications due to their light weight and adjustable jaw openings. The movable clamping jaw (1) can be easily set to the desired length. The clamping pad (2) is concave on one side and convex on the other and pivots to accommodate the exact contours of the instrument. The sliding jack screws (3) allow the crack to be leveled without the use of additional wedges. The double brass rods (4) are flexible and can be shaped to conform to the curvature of the instrument being restored. Brass clamping pads, clamping jaws and spindles with aluminium thumbscrews. Crack clamps with rubber jaws minimize slipping and possible damages to the fine edgework of the instruments. The use of rubber jaws makes this tool safe and even more usable for all precise restoration purposes.