According to the present invention, a fastener for securing a first board to an underlying supporting member and to at least one other board running adjacent and parallel to the first board. The fastener includes a body portion, first and second prongs, and a flange. The first prong extends outwardly from the body portion for driving into a first board. The second prong extends outwardly from the body portion for penetrating a second board. The body portion of the fastener includes an opening for receiving a connector. When installed, the connector passes through the opening in the body portion and into the supporting member, which supports and underlies the first and second boards. The flange extends outwardly from the body portion in order to maintain a desired gap between the first and second boards. The prongs may have concave insertion ends as defined by two spaced-apart insertion points.