AbstractA one-piece spring fastener is provided for mounting fencing wire or the like to a channel shaped support. In one embodiment the wire is mounted generally perpendicularly to the support and is free to move along its axis relative to the support. The fastener is of a generally "U" shape in cross-section comprising two generally parallel, spaced apart, generally "T" shaped members joined along substantially the entire tops thereof by a bight or interconnecting bridge portion. The top portions of the "T" shaped members in combination with the bight portion form a trough for receipt of the wire and the base portions of the "T" shaped members are generally dart shaped for nonrotational, forced receipt inbetween and retention by the inturned flanges of the channel shaped support. Projections on opposite ends of the top portions are designed to engage opposite, parallel, exterior surfaces of the support when the dart shaped base portions are retainingly engaged between the inturned flanges to prevent rotation of the fastener relative to the support.