Here's a quote from Headquarters: When Mac first introduced this feature, it was called Mac Drive.(1950's) This is a design feature on the box end of a wrench that makes it more effective when working on a fastener.
S/O did go for the patent. When the S/O patent ran out, Mac reintroduced Mac Drive. Most all of the wrenches we sell now have Mac Drive on the box end of a wrench.
tmm
