Abstract: Improvements relating to fire hydrant closures are disclosed in which a cap-shaped cover for the outflow port from a fire hydrant, and a tool for locking and unlocking the cap on the hydrant, is provided. The cap includes a septum-like strong plate which is freely rotatable with the cap, but which is fixed against axial movement relative to the cap. Such septum-like plate, including means for mating engagement with corresponding means at the outflow spigot. The plate further includes means constructed to become engaged by the tool; the tool having a grip portion and a mating portion with a corresponding portion provided on the cap.