I purchased a somewhat expensive name brand Beautyrest air mattress. Its electronic pump is at the foot of the bed, and its electrical cord is shorter than the length of the bed, making an extension cord mandatory (ugh). The plug is polarized.
I grabbed a UL-listed polarized extension cord and tried plugging the air mattress into the extension cord. Much to my surprise, the plug does not go in all the way. It stops going in with about 1cm of the prongs exposed.
Thinking perhaps one of the extension cord receptacles had something stuck in it, I tried the other two receptacles available at the head of the extension cord. Same problem.
I then tried plugging the extension cord's polarized plug into itself: no problem at all.
In all my years, I don't think I recall this ever happening before. Am I not thinking of something obvious? Is this likely a manufacturing defect, or is there something going on that I'm not considering? Is it safe to use a Dremel to grind down the air mattress's plug just a little so that it is still polarized, but slightly more narrow?