Abstract: A manhole cover lock includes a lock body which is mounted to the cover and a lock arm mounted for rotation relative to the lock body. The lock arm is mounted to a pin which is positioned in a passage through the lock body. The pin has a specially shaped head for engagement by a special tool. A nut is threaded onto a bottom end of the lock body at a bottom side of the cover. The lock arm can be rotated with the pin from an unlocked position to a locked position, the arm in the locked position rotated under or into engagement with a support or other structure which underlies the manhole cover. The lock arm is retained in its locked position by being biased upwardly to a position where tabs on the lock arm fit into a slot in the lock body.

Abstract: A conventional sewer grate has a locking mechanism for preventing removal of the grate from its mounting frame by unauthorized persons. The locking mechanism includes a grate hold-down device, a threaded nut attached to the mounting frame below the hold-down device, and a bolt extending downwardly through the hold-down device into threaded engagement with the nut. The head of the bolt is specially constructed so that a specially-formed wrench is required to unscrew the bolt from the nut.

Abstract: A conventional sewer grate has a locking mechanism for preventing removal of the grate from its mounting frame by unauthorized persons. The locking mechanism includes a grate hold-down device, a threaded nut attached to the mounting frame below the hold-down device, and a bolt extending downwardly through the hold-down device into threaded engagement with the nut. The head of the bolt is specially constructed so that a specially-formed wrench is required to unscrew the bolt from the nut.