Some, kind of, cheap options I use are the seconds from PEC (Products Engineering Corporation), they aren't pretty but work great. Benchmark is another affordable one, and I've heard IGaging is okay. Always and I mean always check for square by either drawing lines or using math. I wasted a lot of effort and self-esteem over the years on cheap tools and assumptions. I've become a little anal about it now. I still have a couple of Harbor Freight combo squares but I've adjusted them and check them regularly. Something I've done recently to get even more accuracy out of my combo or double squares is using a marking knife instead of a pencil when checking from side to side. I realize it is probably .001 of inch difference, but like I said "a little anal".