Also known as the True Lover's Knot, the Fisherman's Knot creates two identical knots with one line. Ironically, it's not an incredibly strong knot...
Step 1: Grab ends Grab a hold of both ends of the rope. The end in your left hand is end B, and the end in your right hand is end A.
Step 2: Cross ends Cross end B in front of end A so that the end B is behind the loop and pointing down.
Step 3: Pull end B through loop Pull end B up through the loop and to the left, thus creating a small loop on top of the larger loop below.
Step 4: Pull end B through small loop Pull end B through the small loop from back to front with your right hand.
Step 5: Tighten knot Tighten the knot by pulling end B with your right hand, while holding the part of the large loop next to end A in your left hand. You should now have a knot on the top of your large loop, and end A should be able to slide back and forth to make the loop larger or smaller.
Step 6: Pull end A through large loop Pull end A through the large loop from behind, pull it up, thus creating another small loop on top of the larger loop below.
Step 7: Pull end A through small loop Pull end A through the small loop from back to front, and pull tightly with your left hand.
FACT: A knot also means "1 nautical mile per hour" — sailors used to throw knotted lines overboard and count how many knots fed out per 30 seconds to measure the speed of their vessels.