Bottom Rail

The bottom rail is the horizontal steel extrusion or roll-formed channel that runs the full width of the door along the lower edge of the bottom section. Every sectional garage door has one. It sits flush with the garage floor when the door is fully closed.

The bottom rail does three things. First, it provides the structural backbone for the bottom section, tying together the vertical door stiles on each end. Second, it carries the astragal, the rubber or vinyl weatherstrip that seals the gap between the door and the floor. Third, it has a pair of slotted holes or tabs near each end where the bottom bracket bolts in. The lift cable attaches to the bottom bracket, so every pound of the door's weight cycles through the bottom rail each time the door opens.

Because the bottom rail hits the floor on every close cycle, it absorbs more impact than any other frame member. Dents and bends are common on doors in busy commercial use. A bent bottom rail causes the astragal to seal unevenly, leaving gaps that allow wind, water, and pests to enter.

On a standard 9-foot-wide residential door, the bottom rail is typically a 2-inch or 3-inch steel channel, 25 or 26 gauge. Heavier commercial sections use thicker steel or a reinforced extrusion.

The meeting rail at the top edge of each section works the same way structurally but is designed to mate with the rail on the section above it rather than seal against the floor.