Often found in older vehicles, this fusible link wire protects a circuit in applications where you can’t use a standard fuse. The conductor in the fusible link melts if there’s a short circuit or voltage spike, breaking the circuit to protect the rest of your wiring. Since the conductor needs to be thin enough to melt before the rest of your wiring overheats, choose a fusible link wire that’s four gauge sizes smaller than your circuit. If you’re replacing a fusible link that has burned out, make sure the new wire is the same length and gauge as the old one.