Twist-on wire connectors are used to fasten two or more electrical

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 conductors together. They are a type of electrical connector

Electrical connector

An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...

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Twist-on wire connectors are also known as wire nuts ("Wire-Nut" is a registered trademark of Ideal Industries

Ideal Industries

Ideal Industries is an American company that produces connectors, hand tools, testers, and meters for the electrical and telecommunications industries.- History :...

) or cone or thimble connectors. Marrette or Marr connectors are two other trade names for such connectors. In the UK, they were made out of ceramic and sold under the brand "Scru-it."

Twist-on wire connectors are available in a variety of sizes and shapes and are typically made from plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, with a tapered, conducting metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 coiled insert that threads onto the wires to hold the 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 secure. Twist-on wire connectors are intended to be installed by hand only, and may include molded grooves or blades intended to assist in hand installation. Hex tips or hex-like wings are commonly molded into higher-quality connectors that allow them to be installed with a common nut driver

Nut driver

A nut driver is a tool for tightening nuts and bolts. It essentially consists of a socket attached to a shaft and cylindrical handle and is similar in appearance and use to a screwdriver. They generally have a hollow shaft to accommodate a shank onto which a nut is threaded...

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Twist-on wire connectors are commonly color-coded to indicate the nut's size (and hence, its wire capacity). They are commonly used as an alternative to terminal blocks

Screw terminal

A screw terminal is a type of electrical connector where a wire is clamped down to metal by a screw.The wire is sometimes just stripped of electrical insulation at the end, and is bent in a U or J shape to fit around the shaft of the screw....

 or soldering

Soldering

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the workpiece...

 conductors together because they are cleaner, faster, and allow subsequent removal for future rework.

Twist-on wire connectors are not generally recommended for use with aluminum wire; however, Ideal Industries makes a purple-colored Wire Nut^tm that is listed for such use. Also, most connectors are not rated for wet use (such as exposed outdoors), a special gel-filled connector must be used in this circumstance.