Curb feelers or curb finders are springs

Spring (device)

A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...

 or wire

Wire

A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...

s installed on a vehicle which act as "whiskers" to warn drivers that they are too close to the curb

Curb (road)

A curb, or kerb , is the edge where a raised pavement/sidewalk/footpath, road median, or road shoulder meets an unraised street or other roadway.-Function:...

 or other obstruction.

The devices are fitted low on the body, close to the wheels. As the vehicle approaches the curb, the protruding 'feelers' act as whiskers and scrape against the curb, making a noise and alerting the driver in time to avoid damaging the wheels or hubcap

Hubcap

A hubcap, wheel cover or wheel trim is a decorative disk on an automobile wheel that covers at least a central portion of the wheel. Cars with stamped steel wheels often use a full wheel cover that conceals the entire wheel. Cars with alloy wheels or styled steel wheels generally use smaller...

s. The feelers are manufactured to be flexible and do not easily break.

Hotrods

Curb feelers are still used on some hot rod

Hot rod

Hot rods are typically American cars with large engines modified for linear speed. The origin of the term "hot rod" is unclear. One explanation is that the term is a contraction of "hot roadster," meaning a roadster that was modified for speed. Another possible origin includes modifications to or...

s when a 1950s look is wanted. They are especially popular for cars with whitewall tire

Whitewall tire

Whitewall tires or white sidewall tires are tires having a stripe or entire sidewall of white rubber.-Background:Early automobile tires were made entirely of natural white rubber. However, the white rubber did not offer sufficient traction and endurance, so carbon black was added to the rubber...

s, which easily lose their white coating when scraped against the curb. Sometimes curb feelers are found only on the passenger side of the car, since that is most commonly near the curb when parking. Sometimes they are added only next to the front wheels. Some curb feelers have a single wire or spring, while others have two to increase the area that can be protected. Any particular car may have just one curb feeler installed (as on the pictures) or more if attached near the front and rear, as well as on both sides of the vehicle.

Recreational vehicles

Recreational vehicle

Recreational vehicle

Recreational vehicle or RV is, in North America, the usual term for a Motor vehicle or trailer equipped with living space and amenities found in a home.-Features:...

s sometimes have rubber feelers or metal, antenna-like rods mounted on the lower part of the body that act as feelers so that drivers are warned if they are approaching a curb or other obstruction, thus reducing the chances of gouging or even cutting the tire sidewalls and generally increasing the safety of vehicle operation.

Buses

Bus

Bus

A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...

es are sometimes fitted with curb feelers, which can assist the driver in ensuring that the bus is close enough to the curb to allow passengers to step to and from the curb easily.

Heavy equipment

Today, the U.S. Department of Labor

United States Department of Labor

The United States Department of Labor is a Cabinet department of the United States government responsible for occupational safety, wage and hour standards, unemployment insurance benefits, re-employment services, and some economic statistics. Many U.S. states also have such departments. The...

 Mine Safety and Health Administration mentions that users of heavy equipment can benefit from an analogous accessory:

In the 1950s, cars were often equipped with curb feelers
...Using a piece of 48 inch conveyor belt

Conveyor belt

A conveyor belt consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley...

, 4 to 5 feet long by 4 to 6 inches wide and a couple of pieces of angle iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

, you can make a pinch-point feeler, a warning device for the corners of a continuous miner. This will give a warning nudge to anyone in the danger area, giving him or her about a two-foot running start to stop the machine or to yell at the operator to stop. The belting is stiff enough to hold its shape but flexible enough to give if it runs into a miner or vice versa. The flexibility also allows this "curb feeler" to drag against the rib or be smacked by a shuttle car with little or no damage. A little spray from a can of reflective paint

Paint

Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 will make the belt a visual warning device as well. One or two on each corner will help or put as many as you want.

Motorcycles

Some manufacturers of motorcycle

Motorcycle

A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

 parts make analogous accessories also called "curb feelers". One is a rear fender

Fender (automobile)

Fender is the US English term for the part of an automobile, motorcycle or other vehicle body that frames a wheel well . Its primary purpose is to prevent sand, mud, rocks, liquids, and other road spray from being thrown into the air by the rotating tire. Fenders are typically rigid and can be...

 that has been extended into a protruding peak constructed of lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

. Another is a cylindrical

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 tail pipe extension.

Although different in design from the whisker-like feelers described above, the purpose of these devices is the same.

Electronic sensors

Curb feelers based on optical technology are designed to function the same way but work in the proximity of an obstruction rather than having to come into physical contact with it. As described by one United States patent

United States patent law

United States patent law was established "to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;" as provided by the United States Constitution. Congress implemented these...

:

An electronic curb feeler system uses two pairs of optical sensor units to detect an object located near the front end of a vehicle during parking. One pair of optical sensor units detects an object directly in front of a left portion of the front end of the vehicle while another pair of optical sensors detects an object directly in front of a right portion of the front end of the vehicle. By supplying the operator of the vehicle with the location of the object as well as the exact distance the object is from the front end of the vehicle the operator can avoid hitting the object while parking very close to the object.

Devices such as this, and simpler electronic devices similar to the original wire curb feelers used on cars, are used in the design of various mobile robotic

Robotics

Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...

 devices. One robotics company that does work for the United States Department of Defense

United States Department of Defense

The United States Department of Defense is the U.S...

 uses laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

-assisted curb feeler technology.