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The multipoint gearbox is the metal bar inside the edge of every UPVC and composite door — it's the mechanism that drives the hooks and bolts into the frame when you lift the handle. Every UK UPVC and composite door has one, and every one will eventually fail.
How to spot a failing gearbox. Five symptoms, in order of frequency. (1) The handle feels heavier than usual when you lift it to lock. (2) The handle lifts but doesn't fully engage — door 'locks' but pushes open easily. (3) The key won't turn smoothly once the handle is lifted. (4) The handle won't lift at all — totally jammed. (5) The handle lifts but then won't return to horizontal after unlocking. Any one of these is a gearbox starting to fail; combinations mean you're close to a full failure.
Why gearboxes fail. Three causes. First — wear. The hardened steel parts inside the gearbox cycle thousands of times over their lifespan; eventually the springs weaken, the cam wears or a casting fractures. Most UPVC gearboxes last 10–15 years; older lower-spec ones can fail at 7–8. Second — door drop. When the door drops on its hinges, the hooks no longer line up with the keeps; lifting the handle now requires extra force to compress the misalignment, accelerating gearbox wear dramatically. Third — water ingress. UPVC doors with failed seals can let water into the gearbox housing; corrosion does the rest.
Why DIY usually isn't worth it. Gearboxes are sized to the door — the centre distance between the spindle (handle hole) and the keyhole has to match exactly, and the gearbox length must match the multipoint mechanism above and below. There are dozens of variants from the four common manufacturers (Yale, GU, ERA, Fuhr).
Diagnosis (often free if you proceed with the work). Removal of the failed gearbox (the multipoint mechanism above and below remains in place — only the central gearbox is replaced). New gearbox supplied (Yale Doormaster, GU Secury, ERA Vectis or Fuhr Multisafe depending on what your door uses). Re-fitting and full alignment of the door, hinges and keeps. 12-month parts and labour guarantee. Most jobs are completed in a single visit with no parts ordering.
Common manufacturer types. Yale Doormaster — the most widely fitted UK retrofit gearbox; fits a huge range of older UPVC doors. GU Secury — premium German engineering, commonly found on composite doors and newer UPVC. ERA Vectis / ERA Saracen — UK manufacturer, mid-market, fits a wide range of older stock. Fuhr Multisafe — German, found on quality 1990s and 2000s UPVC installations. Avocet WS and Mila Master — less common but worth carrying for the right door types.
Labour is 60–90 minutes. Travel time (every emergency call is a return journey from the previous job). The 12-month guarantee covers parts AND labour.
Cylinder upgrade at the same time. If you're already paying to have the door dismantled for the gearbox, this is the lowest-friction moment to upgrade the cylinder to TS007 3-star anti-snap. Most homeowners take the upgrade at this point; it's good value.
When to call. If the handle is heavier than usual, call before it fails entirely — replacement while the door still operates is straightforward. If the handle has jammed and the door won't lock at all, it's already a priority call (overnight risk of an unsecured door). If the door is locked shut and you can't open it from inside, it's an emergency. Most working locksmiths in West London, Berkshire and Buckinghamshire will give you an honest ETA, day or night.