Aircraft doors that open inward first
To open an airliner door you have to pull it inwards before swinging it out. It seems an odd, fiddly way to make a door.
Category: Getting about
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Feature. Cabin pressure holds it shut.
A plug door is larger than its frame opening, so the cabin pressure pushes it against the frame. The higher the plane flies, the tighter it seals, and it cannot be opened in flight.
Source: Plug door, Wikipedia.