Ground clips

you shouldnt need a hammer! slide the conductor in and push it on with a screwdriver. i recall them coming in bath fans (80's / 90's).
 
We used to use these when a metal box was mounted on a hard surface like concrete or block and the ground screw hole in the box wasn't raised like most are now. Personally I think they're junk. I would bend the wire over the edge of the box so that the metal cover when tightened would hold it in place.
 
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