The wiring system in an Au Ford falcon.
To install a light on a wing and remove the interior brake light, you must:
Remove the back seat, remove the upholstery trim from floorpan. Remove upholstery trim from speaker cover, unplug several clips holding the wiring down, uncoil ~2 meters of insulation tape, identify your wiring, remove interior light and disconnect at floorpan.
Now the next bit...
Feed new wiring through boot (not fucking easy), poke through special sealed hole in corner pillar, feed wire alongside other wiring to floorpan, connect, insulate, replace both upholstery trims, replace rear seat, swear and curse that it was so hard.
Finally, enjoy looking like a ponce with shiny new wing on boot.
Would have been easier to put Red Bull in the petrol tank.