This is a durability and security rating that is issued by ANSI. Specific security features and the durability of the product (the expected number of “cycles” or operations the product endures before wearing out) determine its grade. Grade 1 locks are very heavy-duty and are the only ones suitable for high-traffic public areas. Think of Grade 1 locks as “industrial strength.” Grade 2 locks are “commercial strength.” They are suitable for areas with moderate traffic, such as the employee-only areas of an office. Grade 3 locks are suitable only for residential applications. They will only last in a low-traffic area where people are not likely to abuse the product or treat it roughly. Professional locksmiths can be sure that you get the correct grade of hardware for your particular application. Higher grade locks cost more, of course, but no professional locksmith (nor any hardware manufacturer) will warranty a lock installed in an inappropriate setting.