Steps to tie a square knot
Take note that a square knot can capsize and come undone quite easily, especially if the rope is of a thicker dimension. Therefore, it should never be used to move heavy objects.
The square knot is known as reef knot outside the United States. It is fairly easy to tie, but is not as reliable; and it simply can't be trusted to safely bind two ropes together. When tied using one rope, it can be trusted to hold or lift lighter goods.

Sailors were known to have used this knot for centuries to reef sails, and the name is derived from the very task. It was also used for tying things aboard ships.

Take note that this knot should not be used as a bend (for tying two ropes together). It is unsafe and can come apart. Avoid tying a granny knot, by making sure that both parts of the rope, the standing line and the free end, exit the knot together. You may use a plastic string or a fabric rope to tie a square knot.
How to Tie a Square Knot
Take a rope
Take a piece of rope. We've used two colors in the diagram to help you understand it better.
Make a simple tie
Take the right end, place it over the left. And wrap it over the other side to make a simple tie.
Fasten the tie
Now, pull up the two ends to fasten the tie. It should look like the alphabet 'W'.
Make a similar knot on top
Next, cross the left end over the right.
Tug the two ends
And make another simple tie.
Your square knot is ready
Tug the two ends. And your square knot is ready!
More About the Square Knot
► Besides being extensively used by sailors for reefing and furling sails, the square knot is also one of the key knots of macrame textiles.

► It was used to tie bandages since the time of the ancient Greeks, and was known as the Hercules knot. In fact, it is still used to fasten bandages, and there is a surgeon's version of the knot.
► The knot has also made its humble presence felt in the world of fashion―it has been used to tie sashes and scarves.

► The reef knot holds great importance in Scouting, and is a part of the international membership badge. The Boy Scouts of America have a mandatory requirement to know the demonstration of properly tying the square knot for all boys joining the program.