The pre-orbital gland is the trench-like slit found on the bare skin around the whitetail's eye.  This waxy secretion give whitetails a distinct identity and contains pheromones that gives away communication amongst each other.  The older the buck, the more he uses his pre-orbital gland to mark licking branches, tree rubs, and authentic breeding scrapes.  They can be used anytime or anywhere and will last longer than a urine based lure.