737-500/300/8000 aircraft doors are mannually armed (and disarmed) manually by placing the girt bar in the floor retaining clips when doors are closed: Slides are manually disarmed when seatbelt signs are switched off on shutdown. TOM aircraft also have a red strap placed across the door viewport (visible from outside) when ever a door is armed. TOM procedures are for all passenger doors to be opened from inside the aircraft only, following a knock on the door from the agent indicating that the steps are safely in position.