Abstract: A bonnet is locked to the body of a valve into which the bonnet screws by a sheet metal bonnet lock which includes a portion that will mate with facets on the bonnet or with the sides of the valve body. Another portion of the bonnet lock is then deformed to mate with the other of the bonnet facets or valve body sides. The portion of the bonnet lock that mates with the facets on the bonnet circumscribes the bonnet such that one portion of the bonnet lock is fixed to the bonnet and the other portion is fixed to the valve body following deformation of the bonnet lock to prevent the bonnet from turning relative to the valve body.