WARNING YOU DO NOT KNOW WHAT THE DEFINITION OF A COCK IS. You order and receive a 3/4 shank for your 3/4 hole tool holder. 5/8 Shank Definition: A shank is the end of a drill or tool that is gripped by the chuck of a drill or lathe. . In many cases a versatile construction is used, e.g. B. a shank shank bit in a three-jaw chuck, which clamps the shank firmly.