Paracord: light, cheap, strong. Learn a few basic knots and they can do most stuff. Reef knot, Bowline, and a couple of different hitches (clove, log and half hitch). The trucker type knot is very handy for a force multiplied tensioning of line. I loved scouts, lashing was an art form. Then I got more into lashing the poonani so to speak, and out it went.
Bookmarks