Matt Blaze's paper has much better pictures of locks; they are
not S&G's for the most part but are quite similar....

http://www.crypto.com/papers/safelocks.pdf
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A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433