A square knot where the second hitch is tied in the same direction as the first, sometimes called a granny, doesn't hold well. It's also much more difficult to untie. Look for the little diamond shape between the two hitches. It'll remind you that you tied it right.

2torial #0540: Learn2 Tie Basic Knots (Continued) Knot 4: 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 together to hold light to medium stress. 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 end that crosses on top (end A) over the other end (end B), and pull it back up again. This creates an overhand knot, which is actually a half hitch in a slightly different form. Step 3: Tie it again, but differently Hold the two ends above and away from the overhand knot. The end that crossed on top (end A) must cross on top again. 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. Step 5: Remember it Here's an easy way to remember this: think of left and right. If, for the first hitch, the end on the left goes over and under, then for the second hitch the end on the right goes over and under. A different way: Think about the movements of your dominant hand--over and under, then under and over.) Knot 5