Abstract: A structural interlock (40) for inhibiting relative rotation between mating elements (20, 42) characterized by a plurality of grooves (50) being formed in one of the mating elements, and a mechanism (60) for producing a nominal contact pressure on the contact area (A.sub.1 thru A.sub.8) between the mating element, which contact pressure elastically deforms the other of the mating elements into the grooves (50), and is less than the material yield strength of either of the mating elements. In the preferred embodiment, the grooves (50) are radially oriented and an applied compressive load produces a nominal contact pressure which is about 80% of the material yield strength.