You will need 3 holes as shown if you are using a hinge with dowels. The holes are: a 35mm and 2 8mm, drilled in a Blum pattern. ( the 8mm holes are 45mm apart and offset 9.5mm from center of the 35mm hole)
If your hinge does not have dowels you will need only the 35mm hole (1 3/8") and you can use screws to fasten the hinge to the door. ( not supplied with hinge)
If you purchase doors from Randy Howse Custom Doors we drill only the BLUM PATTERN, COMPLETE. ( all 3 holes )