Key Locking Sash Blocker Timber & Composite Door & Window Restrictor Sash Blockers are designed to provide additional security for your Timber & Composite doors and windows. They're easy to fit and easy to operate too - just a twist of the blocker arm will lock or release the sash. The arm can also be locked into place using the key provided. They are recommended by insurance companies to help protect your home with additional security. This sash blocker is suited for Timber & Composite doors and windows. Key Measurements & Information High quality cast zinc construction. Easy to fit within 5 minutes. Key locking mechanism to provide additional security. Designed specifically for Timber & Composite door and windows. Complete with fixing screws.