The Oregon® Witness Mark™ is a specialized feature created by Oregon Cutting Systems and built into each cutter on Oregon® professional saw chains. The Witness Mark™ feature enhances the life and value of an Oregon® chain by helping chainsaw users do four important things:

1. Sharpen the chain at its optimum angle

2. Sharpen the chain accurately throughout
    its useful life

3. Keep the lengths of cutter top-plates equal

4. Know when the chain has reached the end     of its life