Yeah, calling it "just an old piece of paper" kinda misses the whole story behind it...

My old boss taught me to take three width and height measurements, top middle bottom. You use the smallest number from each set for the final glass size. That extra quarter inch of clearance saves a lot of headaches on those crooked frames.

Oh man, I was totally a sharpie person for years. I figured it was dark and it's right there. But hearing stuff like @adams.dylan's story about the blue smudges really changed my mind. It's not just about fading, it's about leaving a mess for someone else to fix later. That's just rude. Spending a little more time or money on a real label now saves so much trouble down the road. I get it now.