How to tie a mud knot for a carriage horse:
My version of a mudknot stays in for hours, tight without hurting tail circulation. You need no polo wrap or even rubberbands. I like to use a shoelace the color of the tail hair- but did it with a red ribbon here for visibility. The ribbon is too long, but I didn't want to cut it. You only need a yard. When I used to drive commercial carriages I tied my horse's tail up so that it did not go in the diaper bag and so he still had a flowing long tail for his days off.
You can French braid the tail if you want to be really fancy. Here I demonstrate just braiding from the tip of the tail. Notice how I sectioned the hair so that the two side sections will make a sweep for about the last four inches of tailbone.
When making the braid- be sure to sweep it outward toward yourself and not just straight down toward the ground.
That middle section of hair will probably be shorter and thinner than the other two sections- so you will need to eventually borrow some hair from another section so that all sections of braid finish at the same time.
When you are about 4 inches from the end of the hair- add the ribbon. When you are close to the end of the hairs- make a half hitch with one side of the ribbon around the other piece of ribbon and all the remaining hair.
Fold the braid upwards and to one side- wrap the braid around the tail bone.
Tuck the braid/ribbon through one loop of the braid base and pull it snug.
Double the braid back and wrap it around the tailbone in the other direction until there is no more tail to wrap.
The ribbons now part ways- one goes around one way- the other goes around the other way... wrap the tail once and tie in a bow. If you want it to be invisible- tuck the bow inside.
If your horse has never had a mud you may want to tie his tail up a few times before you hitch him so he is already used to it. There will be a lot of weight at the end of his tail bone and if he hits himself with it he may not recognize it as his own tail. For most horses the mudknot keeps their tail heavy and better behaved, but for some determined tail wringers it just gives them more momentum to swing that puppy.