Your bifold door rides on a bottom guide track that is designed to keep the door moving smoothly. But if your bifold door is not moving on its track smoothly, then there are some things you can check. Make sure the bottom guide track is installed securely to the floor and that it is not bent. You should also check the track to see if there is any large debris on it that could be causing the problem. The wheels in the bottom of your door may be stuck and just need to be freed, or the wheels may need to be adjusted up or down to create good contact with the rail.