In principle coining is a process whereby a metal blank is forged by a single blow between two die surfaces to produce shallow features on both sides of a disc. The analogous process occasionally used for diecastings forms shallow features in a small confined area, usually only on one side of the casting. The casting is located such that the under side is supported and the top surface is struck by the form punch. This process is effective in producing exceptionally smooth surface finishes locally, and can produce undercuts on wall sections that would otherwise require a moving die part. The area of the diecasting subject to coining must be sound and free from surface defects for the process to work reliably.