Hinges and interlocks are made in many types. Adjustable toggle-type fasteners offer an adjustable clamping force. A star grip with internal thread offers a robust mechanism to pull and shut doors. Wing screws offer a convenient handle that can be fastened on to doors and other openings. Among the popular type of locks, the quintessential padlock has a solid brass body and steel shackles, in different dimensions and hook lengths. A variant is the nylon safety padlocks, with its non-conductive properties, best suited for places involving electricity panels and cables. Disc padlocks are noted for their robustness, having advanced features, such as a five-pin cylinder, anti-pick mushroom pins, hardened steel shackles and a stainless steel body. Padlocks are available in various strengths, with a double lock bolting mechanism suiting normal applications. Combination locks are similar to padlocks, but a rotating set of marked or numbered dials replaces keys. Magnetic locks operate on a magnetic system. The system consists of an electromagnetic strip attached to the door frame and an armature plate attached to the door. Passing a current through the electromagnet creates a magnetic flux, causing the armature plate to be attracted to the electromagnet and creating a locking action. Direct pull electromagnetic locks are fail-safe, which are unlocked when de-energised.