The act of tying a mud knot, also known as a war knot or mustache knot, in a horse’s tail is a longstanding vaquero tradition that is still carried out in buckaroo country. This practice serves to prevent long tails from becoming entangled in ropes, as well as keeping them clear of mud and brush.
Step 1:

To begin, divide the horse’s tail into two equal sections. Traditionally, the knot is tied before the horse is saddled up and should be untied before the horse is returned to the cavvy.
[WATCH: Brad Barkemeyer’s Tips For a Healthy Mane and Tail]
Step 2:

Proceed to tie an overhand knot by bringing the left strand over the right strand, then bringing the right strand over the left strand and through before pulling tight.
[READ: Understand Your Horse’s Tail Anatomy]
Step 3:

Take the left strand and wrap it around the horse’s tail in a counterclockwise direction, from front to back. Secure the strand in place and take note of where it crosses in front of the tail for the next step.
Step 4:

Now, take the right strand and loop it around the back of the tail in a clockwise direction, then bring it forward and through the loop created by the left strand in the previous step.
[LEARN: Tail Care for Mares]
Step 5:

Finally, pull both strands downward and outward to tighten the knot. To secure it, pour water (or coffee, as some cowboys prefer) over the knot and tighten it once more.