For checking seat rail wear limits as per FAA Airworthiness Directive 2011-10-09, Effective 06/17/2011
The Seat Track Wear Gauge is designed to check for seat rail pin engagement hole wear on Cessna Aircraft, as required by FAA AD 2011-10-09. This gauge is designed to measure the actual radius wear near the seat stop holes and allows for the .020 upper surface wear permitted by the AD.
Download the Seat Track Gauge Instruction (PDF)
Stay away from this gauge. I maintain 13 C172s that operate over the lower 48 states, Ive received calls from several mechanics using this gauge saying that the seat rails fail the inspection. I ask them to go back and measure with calipers per the AD and then the rail passes. Spruce does sell a better product for this test Part# 12-02861.
Instructions are not good. Waste of money.