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.
Max BrooksWe relinquished our freedom that day, and we were more than happy to see it go. From that moment on we lived in true freedom, the freedom to point to someone else and say โThey told me to do it! Itโs their fault, not mine.โ The freedom, God help us, to say โI was only following orders.โ-World War Z
Max Brooks