The metal tool boxes rattle and have sharp edges, the modern plastic ones don't and are pretty compact. The plastic tool boxes also have small compartments to carry a couple of small spares. I also jamb a rag on top of the tools to stop the rattles.that is interesting, I thought most would have a tool bag or roll of some sort. Tool boxes are awkward to store and rattle in cars. and usually have sharp edges.
The tool bag I have was really good until it feel apart.
So the screwdrivers, sockets and spanners all have there own velcro pockets. I've just added a multi-meter, 27mm breakers bar, packet of cable ties, a bit of wire..... and I need to add one of these 1/4" aldi sockets sets next time I see one on special (it has or the torx, alan and bits in it as well).
they squish into a bag quite well. in a tool box it would be big and bulky and slide around the boot A cosmetics bag like Ken mentions would be very close to the tool bag ?
There is no need to carry a full tool kit, make up a custom kit to suit the that car, such as a couple of spanners, screw driver, pliers. If its an old car points, a spare spark plug, fan belt etc. If its a modern car TDC sensor, pencil coil, spark plug, auxiliary belt etc. You will only need the bits that you can easily repair on the side of the road.