Plot hole: At the end of the movie where David and his friends are attempting to break into Steve's house, David has the door code and attempts to gain access once by using it. Steve then tells his wife and the kids to go hide upstairs and turn off all the lights so nobody will know where they are. Then Steve and his wife go to another part of the house, away from the front door. Then, we hear David and his friends using axes and a big log to try and break down the door, "before* Steve secures the door with household appliances later on. Why wouldn't David have just kept trying the code?
Suggested correction: The reason David can not keep trying the code, is because the door has a lock on the top, and one at the bottom (middle regular lock). That middle lock is able to respond to the key/pass-code system, but the top one is not. In order to get in the house, David would have to be able to enter the pin (which, yes he knows) but with the top lock still locked from the inside he can not get in. I am assuming there is a key slot on the outside where he would need a key, and also I'm sure the family doesn't bother locking the top half of the door as no one else knows the pin (so they thought). And I'm guessing that they never locked it during the day either, and only at night.
