Yokes are typically made in sizes 4″ thru 12″. The size refers to the width of the bow as measured from inside to inside of the bow holes.
To measure your animal, place a stick on either side of the animal’s neck where the yoke would sit at rest. While keeping them parallel, have a helper measure the distance between the sticks. If you have two framing squares you can rubber band them together to create a big set of calipers and take the same measurement.
Most yoke makers will use the bow width to calculate the distance between the oxen in a double yoke but if you feel it necessary, you can measure the widest part of the animal’s belly the same way you measured the neck.
One quick way to check for a properly fitting yoke is to slide your hand flat between the bow and the animal’s neck. On a small yoke, the tips of your fingers should fit. On a medium yoke, the base of your fingers should fit and on a large yoke, the palm of your hand should readily fit between the neck and bow.
More importantly, you should watch how the yoke fits while working your cattle. In a hard pull, the bow should slip between the animal’s shoulder and neck.
If the bow hits the point on the front of the shoulder, the bow is too wide and will cause damage and discomfort to the animal.
The bow’s height should be adjusted so that when at rest the bow is slightly pulling up on the dewlap but not pressing into the meat of the neck.
The esophagus is protected by muscle in the neck but between the neck and brisket it is exposed. Using a bow that is adjusted too low will cause damage and discomfort to the animal.
Inexperienced teamsters have a great tendency to use yokes that are too big and bows that are adjusted too low. It is better to error on the side of having the yoke too small or the bows too high.
Don’t be tempted to skip a size. You can’t expect an animal to give their all with ill-fitting equipment.