Flange, also known as a flange disc or rim, is a component used for connecting shafts to each other or for joining pipe ends; it is also used on equipment for connections between two devices, such as reducer flanges. A flange joint refers to a detachable connection formed by the combination of flanges, gaskets, and bolts. Pipe flanges are those used for piping in pipeline installations, or they refer to the flanges at the equipment's inlets and outlets. Flanges have holes, and bolts are used to tightly secure them together. They are sealed using a gasket. Flanges are available in threaded (screwed) connections, welding connections, and clamp connections. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those over four kilograms of pressure typically use welding flanges. Two flange disks are fitted with a sealing pad and then fastened with bolts. Flange thickness varies with pressure, and so do the bolts used. In the case of pumps and valves, the local parts that connect to pipelines are also made into corresponding flange shapes and are called flange connections. Any connection piece that uses bolts to connect and seal two flat surfaces around the circumference is generally called a "flange," such as the connection of ventilation pipes, which can be referred to as "flange-like components." However, such connections are only a part of a single device, like the connection between a flange and a pump, so it is not appropriate to call the pump a "flange-like component." Smaller items like valves can be called "flange-like components."