Disclosed herein is a plastic fixing device which integrally comprises a shank divided into two opposed shank sections connected to each other at their respective lower ends through a hinge portion, a pair of resilient wings extending away and aslant downwardly from the upper ends of the shank sections...http://www.google.de/patents/US4112815?utm_source=gb-gplus-sharePatent US4112815 - Plastic fixing device
