The Bowline Knot, aka the Boiling Knot, is one of the most used loop knots probably due to it's simplicity and security. The Bowline forms a secure loop in the end of a piece of rope that won't slip or bind under strain, and with no load, can be easily untied. This knot has many uses.
To Tie a Bowline Knot:
Start by making a loop and pass the end up through the loop.
Next pass the end around the main line.
Then pass the end back down through the loop.
Pull the end tight to close the knot. If tied correctly, the loop should not slip or constrict.