A thermal fuse is a device for protecting motors, kitchen appliances, heaters, hair dryers, and power supplies from overheating damage and fire. The thermal fuse opens permanently at a certain rated temperature.
The physical part is usually in a bullet-shaped metal casing with round leads. This type is often found in small appliances, such as hair dryers. In clothes dryers, it is usually housed in a rectangular case with two tab connectors. On a motor, the thermal fuse is usually in a fiber or heatshrink tubing insulating sleeve, attached to the windings with a cable tie or other similar object.
When selecting a thermal fuse, it is recommended that you use a part rated to open at 30 degrees Celsius above the expected operating temperature. If you are replacing an existing one which has blown, use one with the same ratings as the original part.