A sectional door, the most common variety, rolls up and down on steel tracks.
1. Torsion Spring
Counterbalances door's weight so that it can be lifted easily.
Guides door up to ceiling and back.
Rides inside track. Steel ones are noisy; nylon is quieter.
Connects horizontal sections.
6. Lock Bar
Engages with track to prevent door from opening.
Seals door edges against air infiltration.
Vinyl doors have a stiff foam core that provides good insulation.
Fiberglass can look like painted or stained wood, but it isn't as heavy, won't decay, and doesn't dent or rust like steel.
Design options for either material are limited. Colors are subject to fading, but these doors can be repainted or stained..