 Zero ohm resistors, marked with a single black band, are lengths of wire wrapped in a resistor-like body which can be mounted on a printed-circuit board (PCB) by automatic component-insertion equipment.They are typically used on PCBs as insulating "bridges" where two traces would otherwise cross, or as soldered-in jumper wires for setting configurations.The "body-end-dot" or "body-tip-spot" system was used for cylindrical composition resistors sometimes still found in very old equipment (built before the Second World War); the first band was given by the body color, the second band by the color of one end of the resistor, and the multiplier by a dot or band around the middle of the resistor.