“A patented frame that can be shoved out of the window and adjusted to any angle; it is made in different sized from 16 in. x 24 in. to 48 in. x 72 in. When not in use, it can be folded up against the wall and occupies but little space.” — Hallock, 1905. The frame is used in the blueprint reproduction process.
V. I. Hallock I.C.S. Refrence Library (Scranton: International Textbook Company, 1905)