A small plastic cap used to retain a wire. Often found in new locomotives, as it eliminates the need to solder the wires to the decoder/light board
Snoods are used in place of soldering. The connections on many OEM multifunction decoders or light boards look like teeth. Each "tooth" has a copper pad with a hole. The wire is pushed though the hole, and a snood is pushed onto the tooth to hold the wire and make the electrical connection between the wire and copper pad.