square tubing size for

what size and gauge is every one using for  buildin a frame inside the bed when sheet metaling the bed .  like 1x1 by 16 gauge

I like to use 1"x1.5" and anywhere from 16 ga to 11 ga depending on what I'm using it for.

1x1 11guage works great. the 11 guage with give you much better support.

ive always used 1x1 16 gauge  but it also depends how much frameing you do depends on teh thinkness needed