It's been five years since I hacked some IKEA BILLY bookcases to create our built-ins that line the wall in our living room. At the time, we were in the middle of a gut renovation of our bathroom, so I asked my contractor to trim them out with some simple molding and I was a happy camper. It wasn't until months later that it dawned on me I'd missed an opportunity to add ambient lighting at the top. Luckily, I did have the foresight to have some outlets installed, so when I came across LED tape lights at a Black Friday sale this week, I jumped on this vacation-day project. It was super-easy to pull off, and you can do it too.