At least one tool should be kept on board the aircraft - it is a pressure reducing valve that is sandwiched between the brake unit and the hydraulic connector block with longer bolts. It reduces the pressure to that wheel assembly to a figure that will give spin braking but not enough to lock a wheel during normal braking - a figure of about 300psi comes to mind. Last time I installed one was in Doha with an ambient temp of 40deg plus on top of that the captain switched the left packs on and the heat exchanger exhaust made it considerably hotter the result being that I collapsed unconscious after finishing the job.