When a laser is to be set on a flat surface where the laser beam is not centered in the pipe, use model 1237 Heavy Duty Trivet Plate.
Using this system, the elevation of the laser beam can be set by either measuring down from a grade offset hub outside the trench or up from the floor of the manhole to the beam.
The invert plates model 1230 (English) and 1237 (Metric) are one piece cast aluminum support plates that provides automatic selfcentering of the Laser in 250 mm (10 in.), 300 mm (12 in.) or 400 mm (15 in.) pipe diameters.
The invert plates are used along with the 1239 Universal Fixed Pole for setups on the manhole bottom, outside of the manhole or in pipes larger than 400 mm (15 in.) diameter