USB, or Universal Serial Bus, connectors have become a standard for connecting computer peripherals. The standard USB connector can both connect the device to the computer, as well as siphon off some electrical power to the device. The relative simplicity of the internal USB wires does allow for some modifications, and splicing and joining two cables to create an extension is possible with only minimal electrical work. However, if must be mentioned that USB connectors that allow for the joining of two cables are available and are preferable to tinkering with the innards of a cable.
Lay the two USB cables in front of each other. Arrange them so the small side of one is facing the large side of the other.
Cut the connectors off of the two facing sides using the wire strippers, leaving about 1 cm (13/32 inch) of wire. At this point, from left to right there should be one USB cable with a large connector and a cut end, then the other cable with a cut end and the small connector.
Carefully strip the cut ends of each cable to reveal a set of four intertwined wires. There should be one red, one white, one green and one blue.
Trim each coloured wire on one cable to be an alternating length with the corresponding colour on the other cable. This means that one cable will have a short red the other will have a long red. One will have a short blue the other will have a long blue. This avoids any frayed wire touchings.
Strip the ends of each exposed wire using the wire stripper.
Lay the exposed wires on the corresponding colour and drip some solder onto them using the soldering iron. This should fuse the wires together. Do this for all of the colours.
Cover the finished and fused wires with electrical tape to insulate the cable.
The USB technology rarely allows cables to exceed 5 m (16.4 feet). Creating a cable that goes beyond that length may affect the performance of the device.