On many historical celli, the corner joints lie on a circle around the centre (Z) of the axis of symmetry.  The inner distance between the upper f-hole eyes should be between 90-92 mm, but in any case should be the width of the bridge feet. The notches lie on a line through the intersections of two circles, the centres of which are at the top and bottom edges of the f-holes. The centre line of the notches is 400 mm from the top edge. The top edges of the lower f-hole eyes should lie below a line through the lower corner junctions (Hargrave, 1987; King, 2004; Lardon, 2020).