A terminal release tool is a set of thin metal keys used to disassemble automotive electrical plugs. Wiring harnesses use plastic locking tabs inside each connector pin cavity to hold the wire terminals secure. If you try to pull a wire out of a plug, the tab locks it in place. The terminal release tool slides into the face of the connector, lifting the tiny plastic or metal lock tab so you can pull the wire and terminal out from the back without tearing the harness.
Using a paperclip or a tiny screwdriver is a common hack, but it often bends the metal terminals or snaps the delicate plastic locks inside. The release tools come in different shapes, including flat blades, round tubes, and double-sided forks, matching standard connectors like Deutsch, Weather Pack, and OEM terminal blocks. Always use the key that fits the pin slot precisely to avoid stretching the contact pin.