Zombies will try to scale any surface no matter how unfeasable or even impossible. In all but the easiest situations, these attempts have met with failure. Even in the case of ladders, when simple hand-over-hand coordination is required, only one in four zombies will succeed.
Unlike the escapee, your team of hunters will be out during the brightest, hottest, most excruciating part of the day. Make sure each hunter is well supplied with water and antisunstroke accessories.