The primary punching tool that can be used to create precise holes in sheet metal or plastics by hand to enable, for example, the installation of fixing screws or components, such as jack sockets or potentiometer control knobs, is known as a plate punch. A plate punch operates by using force to pierce sheet metal or plastic with a circular tool called a punch. Initially, a hole is drilled through the sheet metal or plastic to allow the user to connect the punch and a corresponding circular piece or die using a nut. Then, using the force created when the user grips the operating handle of the plate punch, a rod or ram forces the punch into the die (which is mounted on a bolster plate), shearing the metal and creating the required hole. To facilitate this, heavy-duty plate punches are constructed using high-tensile steel, and are fitted with a hydraulic chamber that significantly increases the amount of force it is possible to exert by hand. Prominent manufacturers of plate punches include Alfra and Ruko.