What is This?

[Dan West]

This was in my Granddad's tools but I don't have a clue what it is. Any ideas?

[Bill Houghton]

Used for setting the revealed width of clapboard siding (which, being tapered in thickness across its width, has no "natural" reveal like shiplapped wooden siding).

Never used one, but the theory's neat.

[Ryan Cathey]

Show us more of the things in your grand dads tool chests! lol

[Dan West]

Cool, I had no idea!

Dan