Saw not cutting stright

[Toolmaker51]

I do almost exactly what Frank S uses. Mine is 5/8'' round stock about 7'' long. 2 #8 screws secure separate clamp. It fits entire blades, from 1/2'' to 1 1/2'' wide, and relief for teeth in both halves. 1/2'' is for my small power hacksaw.
I raise saw frame as if 6'' stock was in the vise. Clamp the bar on and get it vertical [front to back] with a solid square. The round shape creates somewhat a knife edge for the square and very easy to see discrepancy.
It's at work and I'm at home...I'll post a picture come next week. There was NO such internet thing when I made it.