Thermador CHMHP366W Installation Instructions Manual page 6

5. Insert the complete duct cover at an angle and swivel
toward the wall.
6. Carefully pull the top part of the extension upwards.
Screw the left and right sides of the extension to the
mounting bracket with the supplied stainless screws.
Page. 6
7. From inside of hood, screw the supplied 5/8'' (16 mm)
sheet metal screws through the holes on each side
and along the front into bottom of the extension.
Screw quantity is dependent on hood size.