Human Environment

jack handle

A jack is a mechanical device used to elevate the axle of a vehicle so that one wheel is raised off the ground, enabling one to access and change the tire. In simple car jacks, a handle is used to turn the springs of the mechanism so that the device can raise the axle. The handle, which resembles a crowbar, is also used to remove the hubcap if the wheel has one.

electrical transmission lines

Electrical transmission lines transport electrical energy from power plants to substations. From the substations, electricity is then distributed to local users via power lines. Because the initial journey from the generators to the substations is considered bulk power transmission, electrical transmission lines must be able to carry high loads of energy. This is accomplished by wrapping cable strands of aluminum alloy, and sometimes copper, with strands of steel for reinforcement, and then breaking up and increasing voltage with circuit breakers and transformers in order to reduce resistance as electricity travels across the lines.

horse trailer

A trailer specifically designed for hauling two or more horses behind a vehicle. It can also be adapted to carry feed, equipment, and to even heat or cool the animals inside.


A piece of flat, U-shaped iron that is attached to a horse's hoof. Horseshoes are nailed to the hard surface of the bottom of the hoofs, reducing the risk of injury or wearing down, and allowing for long horse rides on a variety of terrains.

Because horseshoes were so ubiquitous at certain points in history, their shape provided the nomenclature for elements in the natural environment. For example, sharp turns in trails, roads, and rivers have been called oxbows, doglegs, and horseshoe bends.


Slug is a vernacular expression often used to describe bullets. Slug is also a specific reference to a bullet without its cartridge. The cartridge of a piece of ammunition contains the casing, which holds the gun powder and the slug, whereas the slug consists of the metal projectile only.

long-barreled rifle

One of the first firearms to be used in warfare, the long-barreled rifle is characterized by its extended barrel, and is an early example of modern rifling technology in which spiral grooves inside the barrel's bore allow for greater accuracy and increased stability of bullet trajectory. It used to be a common personal weapon utilized in warfare, but now is mostly used for hunting.


Sometimes referred to as the "safety button" or "catch," on a firearm the safety, when engaged, prevents the firearm from accidentally firing. In order to discharge a round, the safety must be disengaged, enabling the firing mechanism to work.

spark plug

In an internal combustion engine, the spark plug is a small device that produces electric sparks when the ignition key is turned. The electric sparks ignite the air/fuel combination in the combustion chamber, initiating the combustive force that powers the engine.

rifle rack

A shelf or set of hooks fitted to hang a rifle on. Rifle racks can be kept indoors or installed inside vehicles. In police or military vehicles, for example, they are usually mounted in a somewhat concealed place and yet within easy reach, often either in the front, above the windshield, or in the rear of the car, over the back window. On the other hand, it is very common to see rifle racks installed in the cab of pickup trucks, up behind the bench seat.


A bundle of blankets and bedding materials that have been rolled up and tied together so that they can be transported from place to place. A bedroll can be easily rolled out and used for camping outdoors or sleeping on the floor, and then rolled back up. These days, lightweight sleeping bags have replaced bedrolls, but the principle of a transportable bed is the same.


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