I wish floor receptacles were made with "No-Lose" screw covers - you know some sort of spring-loaded twist-open cover or something.
At my old univ. library, I remember a bunch of floor receptacles with missing screw-covers.
These receptacles would be installed for use with lamps on study tables. But of course every so often, furniture would be rearranged and the unused receptacles would be left uncovered. Lord only knows what the maintenance men did with these aluminium pellets.
Would pose a nice tripping hazard for women walking in high-heel shoes.