Cast iron piping was customarily designed with a person spigot end(plain) and 1 socket or hub finish(cup shaped). In use, the spigot of one segment was positioned into your socket of your previous 1 and a hoop of oakum was forced down in the joint by using a caulking iron. http://tubing-fitting91122.bloggin-ads.com/12203628/a-simple-key-for-pipe-fiting-unveiled