Before I found ArtGarters, I messed around with a lot of different ways to protect framed photographs in transit. Cardboard between the frames (scuffs the faces), foam-core between (same deal), carpet, you name it. Then a friend recommended these handy padded corners. They come in four different sizes, are connected with stretchy elastic, and provide just enough padding so that you can stack several frames tightly without busting up the corners. [She’s no longer marketing these, which is a shame.]
The padding helps separate them just enough so that the frames don’t rub on each other. They are cheaper to buy from Nettie Myers at Mosaic Mind than they are to make yourself. We did make a couple similar ones out of headliner material (the stuff that pads the roof of your vehicle) for some odd-size panoramas, but discovered that it was easier just to get them ready-made.
You can leave them on the frames while hanging work pre- and post show, and they make it a little easier to set work on pavement without fear of dinging up a corner or the bottom of the frame. They are a bit pricey, but you’ll get a bit of a break if you buy in bundles of 5 each.