"Existential Angst" fired this volley in
:

If you need 4x4x1/2, AND you need a sharp corner, I don't think a
machine shop would charge too much to square the inside/outside
corners of structural.

And for what MSC/HD charge, you could get whole lengths from Hadco or
other alum suppliers.

I have a machine shop, and I needed only 4' of the heavy angle, and the
next morning.

Since I live in the boonies, not near any major cities, MSC was the
supplier of choice. In truth, they were only about 20% more expensive
than most on-line suppliers, once you figure shipping (which was a flat
$8.95).

But the OP who asked the question didn't need anything that stout; I was
ribbin' him about whether or not 4x4x1/2 would be big enough to heatsink
one TO-220 transistor or regulator.

For standard architechtural shapes in small sizes, MD is the way to go.

LLoyd