I know you are supposed to be able to push a screwdriver into a slot "under" the wire, but this old (late '70s?) Slater light switch has different slots than I see in all the examples. They are more like recessed holes 1/4" square and are beside, not under the wire hole.
Am I supposed to push on the metal piece? Do I need to get the screwdriver between the two pieces of metal I see at the bottom of the hole? something else? I've tried pushing as hard as I can in different places but the wire doesn't seem to release.