US Patent 7661339 Driving surface configuration for hand tools

A wrench includes a handle and an open-end with two jaws and each jaw has a driving surface. Each driving surface has a contacting area and two yielding areas. The contacting area is located between the two yielding areas and includes a contact portion and two notches. The contact portion is located between the two notches, and two extension areas each are connected between the yielding area and the notch corresponding thereto. A corner is formed at a joint area of the contact portion and an inside of the notch so as to bite a rounded fastener head. The contact portions are matched with straight sides of a normal fastener head.