Abstract: A fastening device and method is disclosed for use in fixedly attaching a single-ply roof membrane to a roof structure of a building. The device comprises an elongated member formed with spaced-apart, upwardly extending arms forming an elongated channel therebetween. The elongated member is positioned on the roof surface and is fixedly attached to the roof prior to installation of the single-ply membrane. The elongated member may also be used to rigidly fix the roof insulation to the roof decking. A separate elongated plate is inserted into the elongated channel after the single-ply membrane is positioned over the roof surface. The single-ply membrane is positioned over the spaced-apart upwardly extending arms and lies within the elongated channel formed between the arms.