If I just want some cheap material for a project, I often consider using softwood (meant for framing and construction uses) dimensional lumber. In case I pass by a Home Depot store and I have to pick up some scraps by the side of the road, what grade are those scraps? What kind of grades of lumber do contractors usually throw away?
Do they generally stock No. 2 or No. 3 grade lumber? Do they even carry No. 1? Is a stud always a No. 2?
Without relying on the lumber to be graded and labeled correctly, what factors can I look for to estimate the grade myself? Is it absence of knots, or just general appearance?