An improved threaded fastener is provided with a shank, a head connected to the shank, and a thread form on the shank terminating below the head. A plurality of lugs are provided above at least a portion of the thread form and are circumferentially disposed under the fastener head around the shank seriatim from a first lug to a last lug. Each lug defines an exposed engaging margin extending from the fastener shank at an acute angle relative to the longitudinal axis of the fastener. The maximum radial dimension of each lug progressively increases from the first lug to the last lug while a corresponding maximum axial dimension of each lug progressively decreases whereby the acute angle becomes progressively greater.