(This is a post by James Haggarty, not Laura, who knows nothing about knotting.)
When first attempting to make a rope halter, one finds dozens of written and video tutorials. Unfortunately, almost all have the same two mistakes. From the AQHA online guide to many of the university extension papers, they have left out one important step and have used an incorrect name for one of the two knots.
The Missing Instruction:
The various guides state that you find the middle of the rope, make an overhand knot and then a second overhand knot xx inches to the left. Then follow the rest of the instructions. If you do this, you may find that one of the two strands is too short to tie around the back of the horse’s head.
According to ListentoYourHorse.com, and with which I agree, the following is an important step and will save you hours of aggravation and money.
“Fold your length of rope in half, so you have 2 pieces of rope of equal length. From the mid-point, move 3 feet (or 1 metre) to the RIGHT of the mid-point. This point is your new “middle”. And the left piece of the rope is now 6 feet longer than the right-hand side piece.
Note: For a horse-sized halter, you would move 2 feet to the right of the mid-point; so your left piece of rope is 4 feet longer.”
One cannot find other references to the double overhand knot in other tutorials. In fact, the real double overhand knot is completely different. This knot used in halters is more widely known as a Matthew Walker knot, or more specifically a two-strand Matthew Walker knot. There are many excellent tutorials and videos on the Matthew Walker knot.
And finally, although not an error, many of the instructions on making a Fiador knot are confusing. The video tutorials by the KnotGirlz on Youtube are excellent and can help clear the fog.