It is important that the boot and indeed door lock are working properly. The use of remote central locking means keys are seldom used to open the boot. This irregular use of the key in the lock over long periods of time can result in corrosion and seizure of the lock mechanism, this can become a big problem if the central locking or vacuum pump fails and the boot can’t be accessed via the key. If the key can’t enter the lock fully then some of the levers are seized or the key you are using is not the correct key for the lock. Probably, in 99% of cases, when the key wont turn in the lock there is nothing broken, bent or worn inside the lock, it is just that the mechanism is bone dry and corrosion has built up, adding to the problem, lubrication solves that. The condition of the lock in Picture A looks a lot worse than it actually was, lubricating it in the way described in the last picture (P) would have solved the problem, without the need to dismantle the whole unit. This boot lock is non-electric on a 1994 C180 = W202 and is Locked/Unlocked by the vacuum pump or by the key. After all the components were cleaned up, the only lubricant I used was thick grease, every thing that moves, slides or rotates was given plenty of grease. Tools required; Work on the kitchen table over an old towel, to catch any small components, springs etc that may be dropped Fine sandpaper to wipe the brass levers, don’t over do it, but clean them just enough to allow them to move freely in their slots. Sewing needle for clearing out slots. 1 Spanner or socket, 12mm. Needle nose pliers. Small screwdrivers. WD40 Thick grease Allow yourself plenty of time, not a job to be rushed. Pen and paper to keep track of which lever belongs in which slot when dismantling the lock barrel. Dec Edit, anyone know why these pictures don’t appear?