A bifold door rides along the bottom guide tracks and in the door header. The design of your door header depends on the manufacturer of your door. When you are shopping for bifold doors, make sure you investigate all of the different bifold kits to determine which header you prefer. The header needs to be sturdy and the area where your header will be installed needs to be sturdy to insure proper installation. There may also be local building codes that dictate what kind of header you can have and what rooms you can have bifold doors in. Check with the local zoning board before buying and installing bifold doors.