On the horse stall signs “hands” is part of the description, such as 14.2 hands or 15.4 hands.

Horses are measured from the ground to the horse’s withers (at the shoulder blades, about where the mane ends on the back).

The hand is a four-base system of measurement. If you measured a horse in inches, 64.8 in. would not be described as 16.5 or sixteen-and-a-half hands, but 16.2, while 68 in. would be 17 hands high (17hh), not 16.4. To keep it simple, fractions are rounded up, so you would not get a number like 16.2-and-a-half.

But why are horses measured in hands?  A four-inch hand, unsurprisingly, is roughly the breadth of a man’s hand, with or without the thumb, a unit of length which can be traced to the ancient Egyptians.