Capt. Pierre's Loop Knot

After many years as a professional fisherman, I still use the very first loop knot I learned as a child. It's easy and quick to tie, and won't slip once tightened down.
Holding the line between your left thumb and forefinger, loop the line back and hold the crossover point. Make the second loop in the opposite direction, forming a figure-eight. Make this loop the size you want your finished loop to be.
Still holding the crossover point between thumb and forefinger, make a third loop around your thumbnail, from bottom to top, pinching all lines together. With your right hand, reach from the bottom up through the first loop and grab the second loop. Pull the second loop to the right, back through the first loop, pulling on both ends till snugly tightened.
- Capt. Pierre Pierce, Fort Lauderdale, Florida