A Secret Weapon. Lumix M4/3 14mm

Back on December 12, 1986 - so my handwriting tells me -, I bought a little paperback book titled simply, Woodwork Joints, by Charles H Hayward.  
Mr Hayward was a very big deal, and contributed mightily to the knowledge which old-school tradesmen like him could pass on to future generations of craftspeople. Here is a link to the Wiki article about him and his many accomplishments.  I notice that Woodwork Joints was first published in 1950.
As I was trying to figure out how to cut the tricky joint depicted in Friday's Blip, I turned to the book. Back when I was making  The Contraption, I copied the little jig which guides a chisel at exactly 45° to cut the miters accurately.  I have pressed it into service for this project, showing both my version of the jig, and the razor sharp German chisel I keep exclusively for this task, atop Mr Hayward's exquisite technical drawings used to illustrate his methods.