Those lousy folding doors on the closet. You can’t get them open, you can’t get them closed.
A bifold door is one that is hinged in the middle and folds to open and close. In most cases, a simple adjustment will correct a sticking bifold door. Sometimes the bracket is just loose and needs to be moved and tightened. Take a look at the illustration.
Often the hinge mechanism becomes loose, the door drops down, and the door begins to rub. The fix is simple if you understand how the hinges can be adjusted.
Take a look at the side and top of the door. Is it aligned in the opening, or is it tipping down and rubbing? If it is tipping, you can adjust the pin/hinge at the top of the door and frame. Normally there is a bracket at the pin which you can loosen/tighten with a screwdriver. Tip the door up to the correct position and tighten the screws.
With the pin in the right location, the door fits squarely in the frame and operates easily.