Greetings, n5pwg!
There are many "friction" hitches used by treeclimbers,
so your question can't be answered with any surety without
further information (unless there is some strong indication
by the military reference --I'd guess "Blake's hitch" or
"tautline" (and a different "t--" than Boy Scouts use, this!)).
For a good read about the "Genealogy of Climbing Knots",
read that like-titled paper by Mark Adams (and the years-later
"Climbing Hitches -- Addenda & Corrigenda"), which appear
as, resp., the 18th- & 13th-listed items via the site linked to
below:
www.treebuzz.com/articles.phpBtw, when you say "plastic rope", I imagine either of the
monofilament, usually bright-colored poly-propylene/-ethylene
ropes; but what arborists use is multifilament polyester or nylon.
--dl*
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