Looks like you nailed it Dan. When I set the blade even with the end of that bar I was within 1* of 25 and when I set it at the 30* mark it was within a degree of 30. Thanks. That had been bugging me for a while. I never thought about it as one leg of a triangle and the height of the guide as another.
BTW, it actually is a pretty honing guide. Plane blades are wide enough to be stable with only one roller under it and it wants to keep the angle across the end of the blade very well too. From the little bit I've been able to find out about them they may be slightly collectible.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
Last edited by Cherryville Chuck; 09-19-2015 at 08:50 PM.