Release able taut line hitch. Make 3 passes around the rope instead of 2 heading toward the tie out point, then use a
bight for the outside half hitch instead of the bitter end. Like
a bow on shoe laces. Easier to undo in cold or wet conditions
or when using loosely woven rope. A Northwest Outward Bound favorite for tarp tie outs.

Bowlines used for critical conditions need a backup safety knot
as they can become untied with rope movement.

You tube knot tests.

Flat overhand knot (tied like the joining knot for rappels)

dry with backup knot
http://www.youtube.com/watch?v=vVTvsUJ6c...&playnext=1

wet
http://www.youtube.com/watch?v=0XZHZpNqF70&feature=related

Figure eight tested to failure.
http://www.youtube.com/watch?v=8_nU_HSqS8Y

Prussics
http://www.youtube.com/watch?v=WNyilCyqJyE
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