Locking a door with a chair is a simple and effective way to prevent someone from entering a room. It can be used in a variety of situations, such as when you are home alone and want to keep your door locked, or when you are traveling and want to secure your hotel room door.
To lock a door with a chair, simply place the chair under the doorknob. The chair will prevent the door from being opened from the outside, even if someone has a key. This is because the chair will block the doorknob from turning.