If it is a serious bite you growl (which is what it seemed to be to me) I would seek the help from a behavorist.

This is a toughie without being able to actually see how he reacts & w/out much knowledge on the dog itself.

Has he been doing this since the very first time he was in the kennel?
Has he ever been fenced in before?
How long have you had him for?
How old is he?
Has anything ever happened while he was confined before?
Does he have seperation anxiety?
Has he ever had any other behavioral issues before?
Does he act beszerk in there when you walk away or when he can't see you?


Maybe you could give him a kong or another toy or treat thet he fanicies that will keep him occupied for a few minutes when you first put him in there. It should help distract him for you to latch the gate.
But I would really look into this further then just the cover it up w/ a treat trick if he is in fact acting aggressivly towards you.