In the U.S. flanges are either threaded or welded onto the pipe. Some square tapered bottom bracket axles are threaded at the ends and use nuts. Press fit inserts are internally threaded and have a knurled outer diameter. It is titled&colon; "Standard Specification for Carbon and Alloy Steel Externally Threaded Metric Fasteners". The front rod gland is usually threaded into or bolted to the cylinder barrel. The Schrader valve consists of a valve stem into which a valve core is threaded. In machined pieces, the hole is most often threaded. Precision would allow better working machinery, interchangeability of parts and standardization of threaded fasteners. Often the rod is threaded to allow adjustment with a screwdriver. It could be fitted with a silencer using its threaded barrel. An archwire will be threaded between the brackets and affixed with elastic or metal ligatures. Flexible tubing was threaded through the pile of boxes of explosives. It is not threaded due to its corrugated shape, although some fittings might be. They can be either internally threaded or externally threaded. It is a kind of threaded insert.