can be difficult for the young and elderly to operate. For this reason door handles in most American commercial and industrial buildings and in many households are lever-operated, rather than a knob, as the lever does not require a tight grip. Levers are also beneficial on doors with narrow stile widths where the reduced backset leaves insufficient space to comfortably turn a door knob. Most household door handles use a simple mechanism with a screw-style axle (called a spindle) that has at least one flat side, which is passed through the door jigger, leaving some length exposed on each side of the door to which the handles are attached. Some handles are attached on both sides by screwing or sliding them directly onto the spindle, and then securing one or more retaining screws (set screws) through the knob perpendicular to the flat of the spindle. Handles that lose traction can frequently be repaired by replacing or adjusting the set screw, which prevents them from slipping on the spindle. Other types of handles, typically used in Europe, slide onto the spindle but are affixed only to the door itself without use of set screws. Types of household handles: Entrance: These door handles are typically used on exterior doors, and include keyed cylinders. Privacy: Typically used on bedrooms and bathrooms; while they are lockable (unlockable with a generic tool), they do not have keyed cylinders. Passage: Also known as hall or closet, these do not lock and are used in hall or closet doors. Dummy: These types are used for ball catch doors or other applications where a mechanism is not needed, but a similar aesthetic effect is desired. Cars Car door handles may protrude from the vehicle's exterior surface or be streamlined into the vehicle's contour (as in a Tesla, for example). In some automobiles, especially luxury vehicles, the door handles may feature a key-less entry pad utilizing either a numerical code, thumb scan or face recognition. Foldables On a balcony whose door has an outside shutter, a special door handle is used on the outer side. The protruding part of such handle (usually ring-shaped) can be folded sideways, so that the shutter can be fully closed without being obstructed by the door handle. Pocket doors A pocket door handle is a recessed rectangular insert, typically with operating hardware called a door pull. Door handles can also be called "handle sets".