I've bent a lot of hard lines in my day, usually with my thumbs and fingers. I finally went out and bought a tubing bender because I see a lot of brake line bending in my near future and I want to make sure I use it properly. What do all of the marks mean on it? I know what the degrees are obviously but on the other side there is O, R, L and another mark I think. So wondering what lining up my mark on tubing with each mark will result in.

Are you talking about the little tubing benders used for bending brake / fuel lines?

If so, I don't have mine here in front of me and can't picture the numbers in my head...I'm sure they are for measuring where you want to start, end your bends, etc.

I have honestly never used them, I just eye ball it and start bending, its really not hard at all once you get the hang of it. Just get you a couple pieces of tube an start playing around with it, it'll come easy....