The Rohn flat base plate is designed to be used with one pier pin, in the hole
centered between the 3 legs.
I've found some of these with an extra hole out near the edge -- maybe for
attaching a rope for carrying. Others I've seen have had four smaller holes out
hear the edge, apparently for bolting to a concrete base rather than using the
The idea of the single pier pin is that the tower can rotate on it when it is
twisting in the wind -- rather than twisting the tower itself.
pix of mine at www.aa1k.us.
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