Abstract: Apparatus for assembly with a bolt or screw upon installation thereof to prevent tampering therewith, including a one piece collar device having an outer annular jacket member with a restricted collar portion and an inner annular washer member detachably joined to the jacket member at the collar portion by a frangible diaphragm. The stem of a bolt or screw is inserted through the collar device and tightened into engagement with the collar portion to cause shearing of the diaphragm to separate the washer and jacket members, the washer member being of a larger axial dimension and smaller radial dimension than the collar portion to permit the jacket member to rotate freely about the bolt or screw and the washer member when the enlarged fastener head is tightened into clamping engagement with the washer member. A cap member fits snugly in the free end of the jacket member to enclose the fastener head.

Abstract: A device for assembly with a bolt or screw upon installation thereof to prevent tampering therewith, including a jacket member for encircling the enlarged fastener head with a collar portion for disposition adjacent its underside to clamp the jacket member in place upon tightening of the fastener and a cap member configured to fit within the jacket member to enclose the fastener head therewithin. A rounded annular channel is formed within the anterior wall of the jacket member and a square annular rib is formed on the outer surface of the cap member to provide a snap-tight interference fit therebetween. The interior jacket wall and the outer cap surface are also tapered at slightly differing angles to provide a supplementary interference friction fit. The snap-fit between the jacket and cap members is sufficiently strong that they cannot be separated using conventional tools without damaging or destroying the members. A special tool is provided for authorized separation of the jacket and cap members.