The Reef Knot
Be a square
A square knot, also called a reef knot, is used to join two lengths of rope about the same thickness. It's quick to tie and untie. Use it when you're in a hurry to tie two ends of rope together.
Like the double half-hitch, it consists of two half-hitches. But it's a very different knot, and you'll see why.
Step 1: Loop
it
Loop the rope around a stationary object (any leg, yours or a
table's, will work fine for practice). Bring the two ends up evenly
on either side. You're now holding two free ends.
Step 2: Tie it
Cross the two ends of rope you want
to join. Pass the left end over the right end, go under, and pull it
back up again.
Step 3: Tie it
again, but differently
Hold the two ends above and away from the overhand knot. Pass the
right end over the left, and then under it.
Notice that end A is now going in the opposite direction from where it went the first time. Push end A over end B, down and through the loop between the two hitches (a hitch is another word for a simple knot).
Step 4: Tighten
it
Pull the knot tight by pulling evenly
on the two free ends. The center of the knot should have a diamond or
square shape. Hence the name. It also should look like two loops
linked together.