Work 1 to be checked is placed with its ends in dual-jet snap gauges 4 and 5 which have metering orifices connected to measuring chambers 3 and 2. These chambers are connected to the branches of U- type manometer 6. If the surfaces of the work are parallel, the pressure in both measuring chambers will be the same and the liquid in the branches of the manometer will be at the same level. The lack of parallelism is indicated by the reading of the manometer.
$3736$SHP,M$