Need help measuring for deck railing posts - what's the best tool for marking angles?

Hey folks, I'm building a deck with angled corners (not just 90 degrees) and need to mark where the railing posts go on the rim joists. I've got a tape measure and speed square, but I'm worried about getting the angles consistent all around. What's the best tool for this? I've seen angle finders and digital protractors at Tool Discount Club but not sure if they're worth it for a one-time project. Don't want my railing looking like a drunk carpenter did it!

lol MasonMark, I feel you! I messed up some angled cuts on a shed roof last month and my boss still ribs me about it. For deck posts, I'd stick with a basic angle finder - the kind with the magnetic base and locking arm. They're like $15 at TDC and way easier than trying to use a speed square on compound angles. Just set it against your joist, lock it, and transfer to your posts. My 2 cents!

Drywall gal here, but I do enough trim work to know angles! Skip the cheap plastic angle finders - they flex. Get a digital one. I use the General Tools digital protractor for crown molding and it's dead accurate. Battery lasts forever too. Pro tip: measure once, cut twice... wait, that's not right 😂 Measure THREE times before you drill any holes!

Thanks both! Matt - good point about the magnetic base, that would stick to the joist hangers nicely. Betty - you're right about accuracy, but this is exterior treated lumber, not finish work. Think I'll split the difference: get the mid-range Swanson angle finder ($25 at TDC this week) and use my miter saw's angle gauge to double-check. Appreciate the help - saved me from buying that $80 digital Starrett I was eyeing!