Each and every grade has a minimum acceptable requirement for ease of operation, pull strength, impact resistance, number of key torque cycles and finish. Most of the residential exterior door locks comes with grades in between 1 – 3. On this scale. Grade 1 offers the highest level of security and considered as the commercial grade. Grade 3 comes with basic residential requirements and whereas the grade 2 in between these two grades. So, choose either grade 1 or 2 to add some security measures to your locks.