You need to know if your door is a canopy or retractable,a canopy door would
normally have about one third of the door protruding past the frame,this
type of door requires a conversion arm for proper operation.A retractable
door works with a pivot action and are best suited to automatic operation.If
you have a separate entrance to the garage fine if not you will require a
emergency unlocking kit incise of power or unit failure.

lastly have a look at Henderson,s Duo range very up todate and very reliable
and no moving chain,also very simple to install. www.pchenderson.co.uk

Alex