There are few options for the cleanroom pass throughs.
Firstly, the pass-through hatch usually apply in those critical cleanroom and for moving small items.
Secondly, you could have a pass-through room or the air lock room, it is a small space room with 2 doors opposite each other. This usually convenient for transfering bigger items with trolleys or carts. Another option would be placing the cleanroom approved plastic air curtains instead of a solid door on one site (facing the cleanroom), this would be much more convenient for the transport operation and normally apply for those less critical cleanroom such as the ISO Class-7 (Fed209E-Class 10k).
The cleanroom process flow and layout is important factors to ensure the smoothness of the traffic flow and the same time maintain a good cleanroom control.