Subaru Legacy 2015 Owner's Manual page 463

9-12
In case of emergency/Jump starting
A) Booster battery
B) Strut mounting nut
1) Connect one jumper cable to the positive
(+) terminal on the discharged battery.
2) Connect the other end of the jumper
cable to the positive (+) terminal of the
booster battery.
3) Connect one end of the other cable to the
negative (−) terminal of the booster
battery.
4) Connect the other end of the cable to the
strut mounting nut.
Make sure that the cables are not near
any moving parts and that the cable
clamps are not in contact with any other
metal.
5. Start the engine of the vehicle with the
booster battery and run it at moderate
speed. Then start the engine of the vehicle
that has the discharged battery.
6. When finished, carefully disconnect
the cables in exactly the reverse order.