The check block is used to establish a reference of zero condition by placing the block on the gage, flat side down, and pushing the Zero/On button. The flat side of the curved block meets the flatness requirement of SAE J442. The simple flat check block is certified flat on one side and meets the flatness requirement of SAE J442.
The curved block can also be used to verify the operating condition of the gage. Place the block onto the gage, curved side down, and note and record the reading on a weekly basis. Readings with a significant change indicate a need for gage service or calibration.