As anyone who has ever played a stealth video game, watched an episode of 'Scooby Doo' or spent a night in a (presumably fictional) haunted house knows, there is nothing cooler than a hidden passageway switched hidden in a row of books.
Indeed, the weird prevalence of these switches in the recent video game 'Thief' seems to suggest that in some corners of the steampunk medieval universe, these things can be bought for less than a fiver at Ikea.
Unfortunately, in our own world, that is not that case. And if you want a hidden passageway, you'll be paying a pretty penny for it because you're probably living in a castle, which are notoriously hard to furnish and heat.
ANYWAY all of this is a preamble to the fact that someone has come up with an excellent, cheap and easily replicable way to make a hidden passageway 'book' switch which instead of opening a doorway into the basement actually just turns on a light.
It's neat. Check it out below, courtesy of Imgur.