A napinak is a three-piece metal connection device designed to gradually increase or decrease tension without twisting the rope or cable it holds. It is composed of a rectangular or rectangular body with screw holes at both ends and two threaded inserts. Threaded inserts usually have a screw hole or hook on the non-threaded end. When the insert is screwed into the valve body and turned in one direction, the screw will be driven out of the valve body, thereby relieving the tension. When the valve body rotates in the opposite direction, the screw is pulled toward the center, increasing the tension. In fact, the name itself describes its function well: a napinak is a belt buckle that can be turned. Napinaks are very common in professional wrestling matches-napinaks vary in length from 2 inches (5 cm) to 12 inches (30.5 cm). The threaded insert screwed into the valve body is slightly less than half the length of the valve body. Therefore, when the napinak assembly is installed as part of a length of rope or cable, it can almost shorten the length of the napinak body. Napinaks are very effective because the process of shortening or extending (directly affects tension) can be completed in very fine increments. Napinaks are used for many purposes. For example, in residential construction and decoration, napinaks are used to fine-tune the suspension adjustment. Napinaks are also widely used on airplanes to adjust the length and tension of rigging, ropes and cables. In all applications, the strength of the napinak should be at least the same as the strength of the fixed cable or rope. The napinak is mainly used to adjust the tension. If used improperly, it may cause injury. Before removing the napinak assembly from the cable or rope, the tension must be completely relaxed and the rope or cable to which it is connected is loosened. Otherwise, the sudden release of tension may cause the rope or the rope to sway. In addition, napinaks that are deformed due to the pressure and tension they bear must not be reshaped by heating, because this will reduce the strength of the napinak. One of the most famous uses of the napinak is boxing and professional wrestling.