When working on computers, it may be necessary to test individual components outside of the case. This could include the computer power supply unit, or PSU. You can "hotwire" a PSU to supply power to individual computers components or to test the PSU itself.
Bend the length or wire or paper clip so that it forms the shape of a tall narrow U.
Locate a green wire on the large 20 or 24 pin motherboard connector from the PSU.
Insert one end of the paper clip or wire into the socket the green wire is connected to.
Insert the remaining end of the wire or paper clip into the nearest socket with a black wire attached. If the PSU is functional, this will cause the PSU to power on. Remove the wire or paper clip to shut the PSU down.
There is virtually no risk of shock from this procedure as the electricity being worked with is DC, not AC. Despite this, it is always safer to use gloves while plugging and unplugging the wire or paper clip.