This knot is used by firemen in case of fires, for example imagine a scene where the ladder on the firetruck messes up, but people need to get down a five story building or more. All they have is a long piece of rope, they can safely get down with a secure knot like the fire-escape knot. So, why not learn it, it's easy to do, and hard to untie if you tie it tightly.
This is from the American Boys Handbook.
Step 1: Get Your Rope
First grab a piece of rope, and bend it like this to make a loop in it. Follow every step to the smallest detail.
Step 2: Twist the Rope
Now make a twist like this, and hold it together.
Step 3: Pull Through the Twist
Pull the loop through the twist you just made, from underneath.
Step 4: Go Over the Split End
Now pull the tail through the loop.
Step 5: Finally
And finally just pull it through as pictured below.
Congratulations you just learned the fire-escape knot.
Step 6: Same Name, Not Knot
This is another knot called the fire-escape knot, this shouldn't be your result.