Sylvester's Problem on Collinear Points and a Relative

A one piece plastic fastener for application to one side of a panel having a generally square aperture and adapted to cooperate with secondary means located on the opposite side of the panel. The fastener has a tapered thin-wall cup-shaped head for engaging said opposite side of the panel adjacent the edges of the aperture when the fastener is telescoped and then rotated in the aperture with angularly offset rigid means adjacent said head traversing the aperture after rotation of the fastener and cooperating with said aperture to prevent unintentional retrograde rotation.