[Blas]

Jumping your car by connecting to the hot side of the starter solenoid on the firewall with the “+” cable works great, but take note of the clearance between a metal firewall and the solenoid terminal it’s usually quite small for the jumper cable clamp. Touching that metal firewall creates a “BIG” electrical short not to mentiona a nasty burn-mark in the firewall. And you’ll most likely be on the other side of the car turning the key when the clamp moves…
The “-“ cable can be connected anywhere on the chassis, and should be connected last. Connecting both cables to battery terminals can cause a spark and the off-gas (hydrogen) from a battery is quite explosive…Proper grounding also prevents the engine from grounding thru the cooling system (i.e. the radiator) which causes all kinds of other problems.