841. The number 16 refers to the number of threads per inch.


These are transfer screws, used to transfer the location of a hole to another work piece.











842. Astro Compass Mk II, from the link: "Used by pilots and navigators to determine accurate true heading by the sun or stars in arctic regions."














843. According to the book Primitives, Our American Heritage these are called snowbirds, and were anchored by the holes to roof edges under materials as slate or tile, they were meant to retain snow for insulation. Others believed they could prevent a layer of snow from plunging down on the heads of pedestrians.


9-5/8" long base:











844. Protectograph Check Writer, anti-forgery device for printing checks in relief:

















845. Insulated concrete form used in building construction, they remain in place after the concrete has cured, and are covered with interior and exterior finish materials:











846. Chainsaw sharpener:










Update:

822. The two photos below of a fender or bumper for a small boat were posted here about a month ago:



Thanks to the Antique Boat Museum for helping to solve this one and for sending this photo of several from their collection:


The fenders were hung over the side of a boat keep it from hitting against objects, most likely used on skiffs similar to these owned by the museum.


































Last week's set is seen below, click here to view the entire post:








More discussion and comments on these photos can be found at the newsgroup rec.puzzles.