Final answer:
To connect wires of the 4-way flat connector to respective black wires on the vehicle or trailer, butt connectors are used, ensuring a secure and conductive connection.
Step-by-step explanation:
To connect the green wire of the 4-way flat connector to the right-side black wire, you would typically use a butt connector. Similarly, to connect the yellow wire of the 4-way flat connector to the left-side black wire, you would also use a butt connector. These connectors are used to join two wires together in a secure and electrical conducting manner and are commonly color-coded to match the gauge of the wires they are joining. Furthermore, it's important to note that color-coding for insulation on wires is important for identifying their purpose within a circuit, such as live/hot, neutral, and ground wires. Notably, the ground wire is often green and may alternatively be yellow or just bare wire.