The channel track guides the rollers and sets the path the door takes as it lifts and folds back. The curve section does the work, taking the door from vertical to horizontal.
Signs it needs replacing
The door catching or juddering at one point in its travel
Dents or spread in the channel
Rollers jumping the track
Sizes and variants
Variant
Specification
Curve
The bend from vertical to horizontal
Straight
The horizontal run
Angle iron
The support section
Fitting notes
Track is cut and set on site. A door that binds in one spot is usually a track alignment problem rather than a roller problem, so both get checked together.