The red line is added to the positive pole of the two cars. You only need to connect the batteries of the two cars in parallel. When you are riding a car, there is no need to start the vehicle on the electric side.
16' Ft Heavy Duty 6 Gauge Battery Booster Cable Emergency Power Jumper 400 AMP
HEAVY DUTY 6 GAUGE 16 FT BATTERY BOOSTER CABLE EMERGENCY POWER JUMPER 400 AMP
HEAVY DUTY 6 GAUGE 16 FT BATTERY BOOSTER CABLE POWER EMERGENCY JUMPER 500 AMP US
HEAVY DUTY 6 GAUGE 16 FT BATTERY BOOSTER CABLE EMERGENCY POWER JUMPER 500 AMP &
Road Jumper Cable Heavy Duty 6 Gauge 10 Feet KC-300 Amp / 1ct
HEAVY DUTY 6 GAUGE 16 FT BATTERY BOOSTER CABLE EMERGENCY POWER JUMPER 500 AMP US