On the cover of “Workbenches: From Design & Theory to Construction & Use” there are a couple low sawhorse-gizmos parked beneath my French-style workbench that look like Munchkins from the Lollipop Guild could have used them to build the set for the “Wizard of Oz.” Those are Japanese sawing trestles that I built five or six years ago based on plans from Toshio Odate’s “Japanese Woodworking Tools: Their Tradition, Spirit, …