Bloodletting - S2-E2
Continuity mistake: When T-Dog is telling Dale that all he found was ibuprofen and cigarettes, he is holding his hand up and they are both looking at each other. In the next shot, suddenly his arm is down and they are both looking forward. (00:22:44)
Answer: The walkers could have knocked them down more than once. There may have been another wave that knocked down the fence earlier and they're going to put it up again soon.
Captain Defenestrator