On Wed, 05 Aug 2009 18:18:07 -0500, spaco wrote:

Here's a link to a neat little tool you can make. You just lay in on
top of a bar, let's say 3/4" square, and draw it along the surface,
holding the legs firmly against the sides of the stock. Even works on
tapered stock.

I think on tapered stock it will make a line a bit closer to the upper
pivot side. Might not be a big error though...