I like the idea of this letter opener/ruler combo. Unfortunately, when I first received it, the edges were square with sharp corners, which ended up tearing a narrow strip of paper out of the envelope and leaving a mess on my desktop.
I took it to my workbench and filed the edges as if I was sharpening a cutting tool. I didn't make it overly sharp, just enough to smooth out the edges, and it works much better now. So, if you're not inclined to do some work on it, this letter opener probably isn't for you.