Wrenches are hand tools that are used to grip and turn things like pipe and fasteners. To tighten or loosen a fastener, the wrench is wrapped around the object and rotated. For a more secure grip while twisting, box-end wrenches have an enclosed head end that fits around the entire head of the fastener. Combination wrenches are used to turn a fastener and have an open end on one side and a box end on the other. Crowfoot wrenches have an open end that allows a brake line or obstruction to pass through, whereas flare nut wrenches have a hole in the wrench head that allows a brake line or impediment to pass through. Threaded pipe and pipe fittings are turned with pipe wrenches. Strap wrenches can grab and turn round or cylindrical objects, whereas chain wrenches handle smooth, round objects with a length of chain. Torque wrenches allow you to apply a specified amount of force to a fastener without damaging it by overtorquing it.