Product introduction:

Garage door cable drum shaft is manufactured to help the garage door remain balanced as it opens and closes with the help of the torsion springs.

Standard-Lift Cable Drums

Standard-lift cable drums are flat for the most part. Toward the outside of the door, the last 3/4 of a turn or so on the grooves of the cable drum is slightly raised. This helps keep the garage door balanced as it begins to open.

Vertical-Lift Cable Drums
Vertical-lift cable drums are taller than standard-lift drums. When the garage door is closed, the cable is farther from the shaft. As the door opens, the cable wraps up on the drum and comes closer to the shaft

So it works for safety,very important for garage door system safety protection.
Garage door can be dangerous task. Garage door springs and cables are under
extreme tension and require appropriate safety precautions. Working with
garage doors and openers could result in personal injury or death. We recommend all installations,
repairs, adjustments, and removals on garage doors be made by a qualified
garage door technician. Any attempts to install, repair, replace, adjust garage
doors or openers are done at your risk.