Deltalock Flush Sash Locking System Features & Benefits Deltalock offers unique corner locking technology. Offers 3 locking points within 100mm of the corner for enhanced security. Provides a night vent option without compromising the weather seal. Will fit most existing flush sash systems. In most cases, existing mushroom keeps can be used. Security corner shootbolt keep is supplied with the extensions. A choice of 4 central gearbox options including non-crop version with centre mushroom cams.Visually distinct - there is nothing else like it! 10-Year Mechanical Guarantee. Patent application pending GB No: 1514768.9Box Quantity: 20. View the full product datasheet here.