Protecting Hardwood Floors with Bottle Caps

I recently broke down an etagere' because the back brace wasn't there. I got tired of it wobbling so I removed it. They come apart in the middle, so I found myself with a perfectly good shelf. I made it into a "end of the bed" shelf for clothes. But...

Not only were the ends of the bottom legs kind of sharp, but when I stretched or the cat laid down wrong, it fell over. So today, I solved two problems.
One, I got an ugly box (soon to be covered) but the perfect size, and filled it with glass and books, anything to weigh it down. Then, I found little protective covers for the legs using soda bottle caps.

They fit perfect and now, even if I have to slide it, I know I am not harming my rental's floors. N-JOY!