Are you trying to figure out what’s wrong with your garage door?

Reading a garage door diagram can help.

When you troubleshoot your garage door problems, and find a faulty piece, you need to know what that piece is called so you can a) go purchase a piece and replace it yourself, or b) call and tell the garage door repairman what’s wrong with your door.

Either way, you need to know what’s wrong with your garage door.

And knowing how garage doors are put together and how they work is critical to understanding how to fix them.

In this article, we are going to explain the three main aspects of a garage door:

  • The frame
  • The moving parts
  • The electric garage door operator


The garage door “frame” is the name we’re giving to the parts of your garage door system that are fixed in place and guide the moving parts.

This “frame” includes the horizontal door tracks, the horizontal door tracks, the horizontal trolley track, the vertical door tracks, the hanger kit, the flag bracket, the jamb brackets, and the bottom rails.

These parts are highlighted in the image above.

These are the parts which are stationary, and direct where the door moves.

Let’s examine each part:



These include door tracks (both horizontal and vertical) and the trolley track. The door tracks along each side of the door are the guides for the rollers on the door, so the pulley system can easily raise and lower the door. The trolley track, in the center of the door and attached to the spring, has a chain on it which moves the door up and down, using the electric garage door operator.

Flag Brackets & Jamb Brackets

These pieces are hardware attach the tracks to the wall and the ceiling, and the rollers to the door, providing firm support for the tracks and the garage door.

Hanger Kit

The hanger kit is made up of pieces of galvanized steel with pre-punched holes in it, which can be used to attached the electric garage door operator to the ceiling and the tracks to the ceiling and the wall. They come unassembled so that you can adjust the height needed for each area they are used.


Bottom Rail

The bottom rail is the lower-most horizontal rail of a door section. On the bottom of a garage door, this piece is frequently a problem if the floor is uneven or it the rail itself is broken or warped. This can allow water and debris to enter your garage, as well as energy loss.

An issue with the framing of your garage door frequently requires the entire door to be taken off in order to fix the broken part. If you are uncomfortable with this task, then don’t hesitate to call a professional garage door repair service.

Moving Parts

The moving parts are those parts which are used to move the garage door up and down.

These parts include the rollers, the hinges, the pulley and cable, the belt, the curved door arm, the torsion spring, the emergency release rope, and the cable drums.

You can see these parts in the above image.

Here, we’ll explain each part individually:



These are the wheels on either side of the garage door, which sit in the door tracks. These enable the door to open and shut smoothly.


Hinges are attached to each of the garage door sections, and enable the door to bend in order to store the open door.

Pulley & Cable

The cable is what is attached to both the springs and the electric garage door operator. This lifts the door. The pulley is used because garage doors are very heavy, and can be upwards of 250 lbs. A pulley lessens the amount of force needed to pull the garage door upwards and let the garage door back down gently.


Curved Door Arm

This piece attached to the trolley, which locks the door onto the chain or belt, enabling the door to move up and down.

Emergency Release Cord

This cord serves to detach the garage door from the trolley and the belt, enabling you to open and close the door manually. In case of an electric power outage or garage door system failure, you can still open the door by hand.

Torsion Spring

A garage door torsion spring is a spring that works by twisting (torsion). When the spring is twisted, then it puts a force on the door, enabling it to be lifted. Replacing or repairing a garage door spring is possible on your own, but if you are concerned in any way, then don’t hesitate to call a professional. A torsion spring holds a lot of pressure, and it could injure you if you’re not careful.

Cable Drums

Cable drums sit on the garage door frame and are where the garage door cable rests. If one of these is broken or has loosened, then your door probably won’t open.

Chain / Belt / Screw

A garage door chain uses a chain (much like a bicycle chain) to move the door up and down. The cheapest of the three options, the chain will last a long time under normal circumstances. A chain will occasionally need adjustment, which is a simple process most people can do themselves.

A garage door belt works the same as a garage door chain, except it has a steel-reinforced rubber or polyurethane belt instead of a chain. While effective primarily for lighter doors (chains work better for heavy doors), garage door belts are the quietest option.

A garage door screw uses a threaded steel rod to rotate the electric garage door motor and wind the garage door up. While the most expensive option, a garage door screw does not need to be adjusted.

If you find a problem with one of the moving parts, oftentimes the broken part can be exchanged for a working one without touching the rest of the door. Make sure you buy the identical part (same manufacturer) you are trying to replace.

Electric Garage Door Operator

The garage door operator is the motor, attached to your ceiling, which opens and closes your garage door. Surprisingly, these were invented way back in 1926!

The operator itself does not provide most of the power which opens the garage door – the springs and the pulley system make up much of the torque required. The motor powers the trolley, which uses the chain, belt, or screw to raise and lower the door.

If you can’t find any hardware problems with your door, then frequently it is an electric garage door operator issue. Call a professional to come out and repair it.


We hope this helps give you an idea of how garage doors work, and which parts do what:

  • Frame
  • Moving Parts
  • Electric Garage Door Operator

Having this information can help you troubleshoot on your own.

Whether you are going to fix the door yourself, or call a professional, don’t hesitate to contact us at G&S Garage Doors with any questions you may have. We would love to answer your questions.

Many thanks to GarageDoorNation and the DIY Network for their beautiful garage door graphics!

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