Identify your garage door type
Canopy garage door
When the door is in the fully open position part of the door(about a 3rd) will project outside of the opening forming a canopy.
Henderson doors use a single coil spring located horizontally across the top of the frame and attached to the door by two steel cables.
Garador also known as Westlands Garador or Catnic Garador has two main systems likely to require spare parts.
The first system was used on MK3C or SS doors use a two springs contained in a spring box installed above the door.
The second system was used for metal framed doors MK4. There are two springs one in each vertical metal frame posts.
Cardale have three main systems .
The first system used on MK2 and MK3 doors use a spring drum mounted at the top of the door.
The second system uses a coil spring which is attached to the door about a 3rd of the way up.
The third system uses a single coil spring located horizontally across the top of the frame and attached to the door by two steel cables.
Retractable garage door
Retractable garage doors use horizontal tracks which are attached to the top of the door frame and suspended from the ceiling to guide the door open. Lifting movement is provided by springs located on both sides of the door frame which pull on the lifting arms in a cantilever action. When open the door retracts into the garage leaving only a small protrusion.