The NIBCO Press System pressing chain adapter jaw is intended for use with 2-1/2-inch, 3-inch and 4-inch chains. The pressing chain adapter jaw is used to compress the chain around the fitting, and maintain proper pipe alignment and uniform crimp. Once secured to the fitting, the chain will not fall off before it is crimped, but yet is easily removed after the crimp is made. When properly crimped, a unique “N” witness mark is clearly visible.