Number three hides generally have five or more holes or large cuts within the hide, ideally within a generally straight line. This would allow them to be cut around later, still yielding a sizable area of usable hide.
A single cut or hole over 6” can be allowed. There might also be grain defects, or a series of closely-located smaller holes that comprise a surface area larger than 1 ft. sq. In general, number three graded hides should at least yield a 50% usable surface area.
Generally, number three grade hides are only purchased by tanners when they have specifically agreed to purchase this grade of hide.