JWR,
I hope all is well. I Was reading the reply to the post on “Constructing In-House Caches.” I have been thinking on this one lately and working on solutions to the problem of attachment, actually came across the solution while working for a contractor on a client’s high end project and trying to build false panels to hide a security control panel.
The solution we came up with was rare earth magnets found here http://www.rare-earth-magnets.com/ or elsewhere on the net as well. you can google it!
If you have plywood paneling you can attach the magnets with a screw to the surface of the paneling and then countersink the magnet on the framing side into the studs, you could also if your paneling is thick enough countersink a larger magnet into the ply panel and use an epoxy similar to the Simpson SET-XP® 10 that can be found at most home improvement or hardware stores, this stuff is sticky and will adhere to the back and sides of the magnet if you rough it up with an abrasive wherever you want the epoxy to adhere. (NOTE: You must countersink the magnet below flush in the panel and use a generous amount of epoxy, or it will not hold.) We used a combination of larger flat magnets drilled through and fastened with screws and epoxy to the ply panels and large cylindrical magnets press fit into holes in the studs, easily retained the large 3/4″ plywood panels, as for a way to remove the panels we put a couple of false electrical and cable outlets on the wall panel, the one outlet was actually live but it gave us a grasping point after removing the face plate and then the panel was easily plucked from the wall. I would suggest making up thickened ply panels at least 3/4″ or thicker to make them appear to be firmly fastened, they will make a different noise when thumped if you just use the 3/8″ wood paneling. Will not be convincing, and will not hold the magnets sufficiently. These magnets are real strong, but don’t skimp on them and you won’t be unhappy, and in this case if you go too big, you may not be able to pull them apart, so don’t get too carried away. – Tom R. in Hawaii