US Patent 7174811 Asymmetric wrench and fastener system

An asymmetrical wrench and fastener system comprising radially extending splines having opposing surfaces whose inner ends are inclined by different amounts with respect to a radius intersecting the respective inner ends to alter the torque between the tightening and loosening directions. This configuration makes it either easier or harder to loosen the fastener than it was to tighten it, depending on the amount the opposing surfaces of the splines are inclined.