A fastener includes a clamp arm which is connected with a base. The clamp arm cooperates with the base to form an entrance into which an article extends. A first locking tab extends from the base into a first opening in the article. A second locking tab extends from the clamp arm into a second opening in the article. When a withdrawal force is applied to the fastener, an arcuate portion of an inner side surface of the clamp arm moves from a position spaced from an outer side surface of the article to a position in which the arcuate portion of the inner side surface of the clamp arm is disposed in abutting engagement with the outer side surface of the article.