Yale Blade espags feature a unique blade or wave locking mechanism which engages the full length of the keep. Designed to sit flush within the Eurogroove. The system also allows separate installation of the keep and lock prior to the hanging of the sash to deliver greater flexibility and efficiency during fabrication. The unique rotating action of the lock provides users with a smooth and easy to close window, with minimum wear to components, leading to a long service life with no loss of compression.