Abstract: An assembly for fastening an insulation batt to a supporting surface. The fastening assembly includes an elongated fastener which is driven into the supporting surface with the head end of the fastener protruding from the supporting surface a distance approximately equal to the thickness of the batt of insulation. The batt is then impaled upon the protruding fastener and pushed down thereon until the head of the fastener protrudes from the surface of the batt remote from the supporting surface. A planar locking clip having a keyhole-shaped opening is then slipped over the fastener head and wedged between the fastener head and the batt. The locking clip is held in place by engagement with the fastener head, and prevents the insulation batt from pulling away from the supporting surface.