Let's make apprentice created enchantments

[Erik_Tyrrell]

Cow Heard's Whip
ReAn 13 (12 uses per day)
R: Touch, D: Conc. (Item maintains) T: Ind.
This enchanted whip, when placed in a doorway or gate less than 4 paces across, wards the doorway against mundane animals who are unable to pass through it. The opening is only warded for as long as the whip is within the opening. Mundane animals are unable to move the whip when it is active.
(base 2, +1 touch, +1 concentration, +5 levels item maintains concentration, 4 levels 12 uses per day)

The rules for a ward say that he target is the thing that is protected. In this case the protected thing is an opening. Whether an opening qualifies as a thing might be matter of debate, but I think it is a reasonable interpretation.