Security Levels Explained To help you chose the right protection for your door Yale products are graded by the level of security they provide. Maximum: Maximum security products comply with the latest British Standards and offer the maximum level of security protection and offer increased protection against common attack methods. These locks should be used on your external front / back doors. High: High security products provide a high level of protection and features for internal doors. These locks should only be used on external front / back doors in conjunction with a Maximum security level lock. Standard: Standard security products offer convenience locking solutions with basic security features for internal doors. These locks are for indoor use or should only be used on external front / back doors in conjunction with a Maximum security level lock.