We go through tons of flat stock in 1/8. 3/16, 3/8, and even 1/2 inch thick. There are generally a bunch of cut off pieces that range in size from maybe 3x3 inches to 12 X 12 inches. Great for making brackets and gussets. We also keep some of the same thicknesses in 1 inch wide to 3 inches wide for the same purposes.
If you go to most steel supply houses you can dig through their "drops" that are left overs and sell at a reduced price. We have one here in town that we would go in periodically and pick through these pieces and buy what we could use. But some idiot customer got hurt and sued them so now they have a policy that no one except employees can go to that area.

No one wants to take responsibility for their own injuries, so they sue.
Actually, practically any piece of scrap you have laying around can come in handy at one time or another.
Don
I know this is a little early but, this site is down more than it's up, so...................... Here's hoping everybody has a great holiday season and my best wishes for a great and prosperous new...
Merry Christmas and Happy New year