We use an aluminum edge restraint made in Michigan, made by Curv-Rite. Here's a link:
http://www.curv-rite.com/prod02.htm
We get it for about $1 per foot. Order 1200+ feet and the shipping is free. I like it because it doesn't flex with the changing temps, is lower profile than the plastics, has a keyway and keys so you can have a single run of edge restraint around your entire pavement, and is extremely flexible.
I can't believe there are companies there that don't use anything. Just asking for trouble that way...
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