The Hydra-Dome lock features a cast iron dome with a protective coating. It is designed to fit over the brass operating centerpost on most hydrants. After placing over the centerpost, insert the special stainless steel security plug into the side of the dome and tighten with the security wrench. The plug will fit into a groove in the centerpost, securing it to the centerpost and allowing the dome to spin freely on the hydrant.
A special wrench fits the plugs which is used to install and remove the dome over the centerpost part of the lock. This denies access to all except authorized wrench users.