This system slides into the accessory tray slot and locks in place.  The rod box is made up of a grid of 17 rods x 17 rods giving approximately a 28 cm square coverage. The aluminum rods are 1/8” diameter x 30.5 cm long.  They slide through a plastic block and friction assembly. Ten rods are anodized black and can be used to locate the center and corners of the fields.  A row of orientation holes are provided for measuring the rod length using the Adjustable Gauge (Item 143-020) for compensation thickness.  The bottom side is engraved 1 to 17 and A to Q for easy identification of rod locations.