US Patent 7797972 Secure fire hydrant cap

A security device for engaging a threaded element includes an inner body configured to engage the threaded element and an outer body operatively coupled to the inner body. A pin is operatively coupled to the inner body and movable between an extended position and a retracted position such that the outer body moves relative to the inner body when the pin is disposed in the retracted position and the outer body and the inner body are operatively coupled for simultaneous movement when the pin is disposed in the extended position.