The sash fastening is made with 3 screws.
Thanks to the adjustable screw , frame can be adjusted vertically 3 mm (+/ -) by using a 4 mm allen wrench.
The gasket pressure can be adjusted 0,8 mm
The screw holes are specially designed in order to prevent the drill in corner hinge to apart from the sash (due to exceeding material that comes off when the screws are fixed)
The 6 mm positioning pins ensures a better lift in the material of the frame.