A knob lock is a common type of door lock that consists of a round knob on either side of the door. It typically features a locking mechanism that can be engaged by turning the knob or using a key. Knob locks are often used for interior doors, such as bedrooms and bathrooms, as well as for some exterior doors. These locks are generally easy to install and operate, making them a popular choice for homeowners. However, they may not provide the highest level of security compared to other lock types, such as deadbolts, which are often recommended for exterior doors to enhance safety.