Is my door suitable for installation? Blair April 02, 2019 10:36 Updated The DB series can be installed on any door between 35 - 50 mm thick. Related articles Do I need to drill holes in my door? What kind of key blank should I use if I need more keys? How do I restore my Alfred DB series to factory settings? What tools do I need to drill holes? Why is Alfred failing to lock? Comments 0 comments Please sign in to leave a comment.