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.
Procure an extra long shade and cut two openings in the end to be used at the top. The openings may be cut square or ornamental as desired, leaving a strip at each side and one in the center. These strips are reinforced by gluing on some of the same material as the shade or pieces of tape.
A shade made in this manner per- mits the air to enter the room unhindered when the top sash is lowered and at the same time obstructs the view of passers-by. - Contributed by Warren E. Crane, Cleveland, O.,
Ill: When the Shade is Pulled Down the Openings Coincide with the Opening over the Upper Sash