On Jun 1, 4:56 pm, "John Grabowski" wrote:
I have used 6/32 hex nuts behind the device strap to keep the device from
being pushed back.

I think this is the best solution - there's just one nut, no worrying
about 3-4 washers; it attaches the outlet solidly to the box which is
itself attached to the stud, so everything is robust; and if the box
is metal, the outlet or switch body is solidly grounded.