From page 729 of the 1953 THE SCOUT annual:
We all know, says Medd, how important it is to keep the Scouter or D.C. in good temper in camp, especially when competitions are under way and everything depends upon the mood in which the examiners wake up in the morning. Many Patrol Leaders, in such circumstances, pin their faith to that early morning cuppa; but what is the good, asks Medd, of offering a D.C. a cup of tea when he has probably spent a restless and disturbed night?
As everyone knows there are different grades and "depths" of sleep, and the sort we must ensure for our Scouters and Commissioners is that deep, dreamless variety which reaches right down into the sub-conscious and is spoken of so highly in the advertisements for malted milk.
The "Medd Auto-Tent-Door-Closer and D.C. Ingratiator" achieves the same result quite painlessly. What happens is this:
Rain falls during the night and runs down the trough into the billy-can, thereby upsetting the balance of the guillotine and bringing the razor-sharp knife into operation. This releases the spring-sapling and unties the super slip-reef on the door curtains. At the same time the vibration on the sapling rings the warning bell to let everyone in camp know rain is falling. The D.C. awakes, hears the groans of less fortunate fellow-campers as they stagger out to deal with the situation, and goes peacefully to sleep again."