bifold
A door, window, shutter, or divider consisting of two equal panels hinged together so that it opens by folding the panels against each other.
bifold: two-panel door that folds in on itself
A bifold is a door or shutter made from two hinged panels that collapse by folding one panel against the other. When opened, the panels stack against each other at ninety degrees, taking up roughly half the width of the opening compared to a traditional swinging door. The hinge joining the two panels sits at the center of the doorway, and each panel pivots on guide tracks at top and bottom that keep it aligned during operation.
Bifolds are most common in closet applications, where space constraints make a full-swing door impractical. A standard bifold for a 36-inch opening uses two 18-inch panels. The bottom guide track is a simple channel that keeps the bottom corner aligned; the top track carries the weight and controls movement. Rollers or wheels ride in the top track, while a pivot bracket at the bottom supports the weight. The meeting edge of each panel typically has a magnetic catch or soft-close mechanism to hold them closed.
Construction and Materials
Bifold doors are usually built from hollow-core or solid wood frames with a plywood or MDF skin, though commercial versions use aluminum frames. The panels themselves are relatively light because they must slide smoothly in the track system. The hinge connecting the two panels is a simple butt hinge, rated to handle the intermittent stress of opening and closing. Track systems are sold as complete kits, with the hardware engineered to coordinate; mixing components from different manufacturers often leads to binding or misalignment.
Problems arise when the top track warps from humidity changes, when rollers accumulate dust and bind, or when the bottom guide track gets bent. A bifold door that rubs or drags at the bottom corner usually indicates that the pivot bracket or guide track has shifted. Regular lubrication of the track and rollers prevents most wear issues. The hinge connecting the panels can loosen over time, causing the door to rack, but this is a simple fix with a Phillips head screwdriver.
Bifolds appear in non-residential applications too, particularly as room dividers in offices and as accordion-style shutters on storefronts. In these contexts, the panels may be wider and the track systems heavier. The name itself describes the function clearly: two folds, one action.