Abstract: A locking device for a rotational based fastener for fastening an object to a substrate, the device including a washer for placement between the fastener head and the object a locking plate for removable engagement to the fastener head to prevent relative rotation of the locking plate and the fastener head, and a flexible, substantially non-elastic integral folded tab connecting the locking plate and washer, the locking plate has a first aperture to receive the the fastener shank such that the fastener head will upon tightening draw the washer into tight contact with the substrate, the locking plate is larger than the fastener head and has a second aperture of smaller or equal size than the fastener head, and the locking plate includes a swagable portion near the perimeter of the second aperture to bridge the fastener head when the locking plate is swaged over the fastener.