This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
In using the ordinary photographic printing frame with a spring-pressure back, the back must be entirely re- noyance, I placed at one end of the frame, as shown in the sketch, a second hinge made of cloth or any pliable material. When the pressure springs are released, the back swings down on this auxiliary hinge, and after changing the papers, it is instantly closed by a slight movement of the hand, making it very rapid and easy to use. - Contributed by Thos. L. Parker, Wibaux, Mont.
Ill: The Back, being Hinged to the Frame, Prevents It from being Mislaid