Roll Groovers are used to make a grooved mechanical joining of two pipes. A small groove is made at the end of each pipe with a grooving machine. A rubber gasket is fitted over the two pipe ends and around it a two-part coupling is screwed together with two bolts and nuts. It is often called a Victaulic Coupling after the inventor of the system. As opposed to threaded joints, it allows for a small amount of misalignment of the pipes or later removal of a section of piping in the middle of a run.