A device designed to slow people down.

In order to prevent your reaching excessive speeds while 'indoors', doors may be installed to act as barriers between rooms in any building.

A handle on either side of the door has to be turned and pulled towards you to open the door. If moving too fast towards the door whilst opening it, your head will safely knock it shut again.

A door provides you both with an opportunity to think twice and reconsider leaving, and a pause in which the reason for leaving may be conveniently forgotten anyway.

Attempts have been made to do away with doors, in a movement called 'Open Plan'. However, this has led to an increase in aimless wandering through buildings, to coffee machines, stationery cupboards and smokers' rooms.

Amongst the other uses to which a door may be put are security, whereby prisoners are rationed to one door apiece, minus an interior handle, and safety, to prevent the inadvertent exit of a forgetful astronaut or submariner.