there is one just beside that one. open up stairs and jump from the top of the stairs into the crack in the wall just below the ledge where you can jump onto. if you do it rite the zombies will walk straight past you and up stairs and get stuck at the back wall upstairs
if your on a game if 2 people go behind you and at the top of the stairs the zombie will not attack them aswell. works better with only 1 person behind though. but if 2 people go into the help room and stay in there the zombies from the first room will all come to you even the window near the help room then they just consentrate on the 2 windows and wall in the help room.