Bi-fold doors come in “pairs” (two or four panels). They are used primarily for the small closets (up to 6′ wide).
Occasionally they are used as a room divider or in a place of regular hinged interior door.
They can be mirrored or made out of wood (like louvered doors or 6 panel type doors).
Repair of bi-fold doors sometimes involves changing their hardware, and sometimes the track has to be changed. Bi-fold doors are usually less robust than sliding closet doors so we usually recommend sliding closet doors for high usage applications. But if the full access to the closet is a must then they are an obvious choice. Another solution to closet spaces and room dividers are accordion doors, which we can also measure and install for you.