snip

That fits with the pinstriper theory. The screw would be to clamp an
adjustable edge guide that you can use to follow an existing stripe or a
contour on the body of a car. Sort of like using a rip fence on a circular
saw. Here's a modern version:

http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemID=1916&itemType=PRODUCT&iMainC at=503&iSubCat=536&iProductID=1916&itemType=PRODUC T&RS=1&keyword=beugler

snip




Yup, I was just going to Eastwood myself to get the link. I have a
couple of those Beuglers for pinstriping.