Manhole keys are designed to safely lift and remove manhole and inspection covers.
They are inserted into the keyway of a manhole cover. A keyway is a slot or keyhole.
Manhole keys are usually sold in pairs because most manholes have two keyways, but single keys are available.
Manhole covers can be too heavy for one person to lift alone. The cover needs to be lifted vertically and laid down on the ground safely.
Manhole keys work by slotting into the keyway. When the key is turned a quarter turn, it locks into place, allowing you to lift the cover safely whilst holding it firmly. You can then move the manhole cover so that it cannot drop or slide back into the hole.