David Nebenzahl wrote:
Eric in North TX spake thus:

Probably a manufacturing error, but if the receptacle has only 2 wires,
there is little point to attaching it to the screw anyhow.

True that; if you look at 2-wire connections to outlets, the metal frame
of the outlet isn't connected to *anything*. The only reason to use that
screw would be if you wanted to attach the adapter to the outlet. It
serves no electrical or safety function.

I was anal enough to check way back when when two prongers were going
out and three prongers were coming in and these adapters were all the
rage, and the ones I checked did have the center screw electrically
connected to the mounting and thence to ground. Maybe varies from brand
to brand.