A convenient place to write the name and number of the paint you used in a roomThis got me thinking that the back of a lightswitch plate is a handy place for engineers to jot down all sorts of information. For example, let's say you've got a heavy-duty dimmer switch for two dozen incandescent tracklights. This is a special switch, designed to take a lot more than the usual 600 watt maximum. Ten years from now, the engineer of that day - who's renovating the place - might've lost your documentation and he or she doesn't know what the actual wattage maximum is. Well, there you go - write it on the back of the switchplate.
is on the back of the switch plate.
Maybe you could hide a lock combination or spare key back there, too. Obviously you'd have to evaluate whether this is worth the inherent security risk (not to mention be careful sticking a conductive key near electricity!) but it's probably more secure than a key hidden under a doormat.
Depending on how public the info needs to be, you might also put a code there that matches a code at the breaker panel...a handy confirmation for what circuit that lightswitch or power outlet is on.
There's a part of me that thinks there's probably a way to expand this concept of "cleverly hidden info that's easy to forget" to other avenues for the expert radio engineer, but at the moment I'm lacking inspiration. When I think of something I'll post here, but if you have an idea by all means please share!