"All antlers have four circumference measurements taken on each main beam. Even a spike buck would have four circumference (in the case of a spike, the circumference would be taken halfway between the burr and the tip of the point). This measurement would be entered four times as H-1 through H-4."

This is directly out of my P&Y Official Measurer's Manual (Whitetail Deer section, page 45). Many here have given the correct answer, which is any/all antlered species will have four circumference measurements. Where you take these measurements depends on the antler configuration you're dealing with.