The Square Knot or Reef Knot (actually, a bend and often also a knot) is included here because it is used so commonly. It is a fine bend for tying shoelaces, packages for mailing, and reefing sails on a boat. But it can only be safely used to bend two ends of the same line or two exactly identical lines together and never in a critical application. Leave that job for the much more reliable Sheet Bend.
To Tie The Square Knot or Reef Knot –
Use the Boy Scout right-over-left, left-over-right method, hold one end in your left hand and the other in your right hand.
Lap the working part of the line in your right hand over the standing part of the line in your left hand and continue wrapping the line until it is in front of the standing part, creating a bight.
Transfer the bitter end you just used to create the bight to your left hand and hold the other end with your right hand. Your line should look like that in A.
Repeat the process starting with the end of the line now in your left hand, as shown by the black lines in B.
You will now have the completed knot with the bitter ends on the same side of the standing parts, as shown in C. If the ends are not on the same side, you have tied a Granny Knot or Thief Knot and it will not hold.
The final step is to tighten the knot by pulling on both the bitter end and standing part on each side of the knot until it is tight, as shown in D.