Frames and supports in 15th and 16th-century Southern Netherlandish painting

CHAPTER I 34 In principle, boards were left at their maximum thickness for reasons of strength, especially when, following cutting, quarter-cut boards had one narrow harder edge, closer to the centre of the tree where the wood was more compact, and one softer thicker edge, closer to the sapwood, and which the joiners avoided thinning more than necessary. In other cases, in particular where the board has been sawn rather than split, the thickness of the panel is regular and the reverse is also smoothed flat, at times summarily with an adze or a gouge chisel or a scraper. Sometimes also, from the earliest times, the backs of panels of small dimensions are planed perfectly level. But it is especially later, and in particular in the 17th century, that this is done more systematically. 3. Measuring and marking instruments Measuring and marking was done using a measuring rod generally divided into six feet (a footed rod) , one end of which was divided into inches, usually 12, sometimes 11, 10 or 9, according to local practice (fig. 6: 48), or a ruler (fig. 6: 49-50) some of which contained a tab notch (fig. 6: 50), a square or a triangle (fig. 6: 43-45). Large squares were held in place by a sort of key slipped into the angle (fig. 6: 45). Longer lines, like those used for sawing, were marked out with marking string (fig. 6: 23) as already mentioned. For other marking, a marking point or wood scribe (fig. 6: 52) or a mortise gauge were used (fig. 6: 51). Compasses of various kinds were used also for measuring and marking. Besides the ordinary compass (fig. 6: 53), there was the spring compass (fig. 6: 54) the spacing of which could be fixed by means of one or two wing nuts screwed on a riveted pin. Callipers (fig. 6: 55) served to measure the thickness of non-square pieces. The precision compass included a graduated guide (fig. 6: 56). Outside/inside callipers or “dancing masters” , were double-ended callipers used to measure inaccessible places such as insides of notches and mortises (fig. 6: 57). For placing large pieces one could use a plumb level square (fig. 6: 43), a sort of triangle supported by a diagonal piece and containing a plumb, serving both as a level and a square. The marking gauge (fig. 6: 51) was used to draw parallel lines and to ensure that the pieces of wood were of regular width and thickness. This marking gauge consists of a wooden rod that passes through a slot in a movable head and is held firm with a key. The rod has a small spike at its top. By running the gauge along one side of a board a line is created parallel to it, thereby ensuring that the opposite side is parallel to it at the desired distance. The mortise gauge has two spikes spaced so as to mark both sides of a mortise or tenon in a single stroke.