Hanging lights from a gap?
I think a bolt with an expansion nut (or coupling nut) would kind of give you the &quot;expansion clamp&quot; behavior you're looking for
Alternatively you could try &quot;hardwall hangers&quot;, they nail into concrete fairly easy.When you're done you can pop them off with a screwdriver and the holes are small enough that I don't think it would cause any issues with your apartment complex