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.
A flour bin, counterbalanced to swing closed at all times, is liable to catch the arm of the one taking out flour. To make it safe, I applied the device shown in the sketch. The bin, at rest, is shown in Fig. 1. The safety catch consists of a stick of wood, A, notched at one end, and is pivoted at B on a small bolt. Two stops, C and D, are located on the side of the box to prevent the catch from being thrown out of position when the bin is quickly pulled out. These stops are nails driven into the box side. When the bin is pulled out the catch takes the position shown in Fig. 2. The catch stick should be a little shorter than the distance the bin is pulled out, so that it may be raised to release the bin for its return. - Contributed by O. F. Fouche, Erie, Pa.
Ill: Automatically Operated Catch to Hold a Flour Bin Out While Taking Flour from It