If you only learn one knot make it the marlin spike hitch. It's simple to tie and leads you right into 4 other great knots.
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How to tie a Spanish Bowline
How to tie a Bowline Knot w/ A Yosimite Tie Off
"The Magic Braid"
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5 Knots You Need to Know How to Tie at All Times - http://itstac.tc/H0yIlM // Bowline // Taut-Line Hitch // Threaded Figure-Eight // Double Fisherman's Knot // Power Cinch Knot
Loop Alien + Tarp + Continuous Ridge Line - rigging a tarp with the loop alien rapid cord attachment and a continous ridge line