A "rule of" provision in your stock plan triggers vesting when you retire. The number it uses is the sum of your age and the number of years you worked at the company before retirement. The company can choose any age for this provision (e.g., a rule of 75, rule of 65, etc.). Under a rule of 75, for example, the sum of your age and your completed years of service must total 75 (e.g., age 65 plus 10 years of service, or age 55 plus 20 years of service). For details, see the section Life Events: Retirement.