Plattekloof locksmith — where the biggest opening in the house is a wall of glass.

Often it is not, and it is worth a second opinion before committing. On these systems the common faults are a mechanism out of adjustment, a handle set that has lost its connection to the gearing, or rollers flattened under the weight of the panels. All three are serviceable items and putting them right costs a small fraction of a replacement, usually in an afternoon.

Throw the handle, then try to lift and pull the panel at the top and bottom edges rather than the middle. If it moves at the extremes, the upper and lower locking points are not seating and the door is being held by the central catch alone. This is the most common fault we find here and it gives no warning at all — the handle feels completely normal.

Usually because the frame has settled very slightly, which is entirely normal in a modern building. A multipoint mechanism has fine tolerances, so a few millimetres of movement is enough to stop the top and bottom points reaching their keeps while the handle still travels fully. It is an adjustment rather than a fault in the door itself.

Almost certainly not. The rollers carrying large glass panels flatten over years under that weight, and the resistance increases so gradually that households simply adapt to it. New running gear and a track service normally restores it completely. The glass, the frame and the locking mechanism are usually all fine.

Where it faces open ground, a slope or a view rather than a neighbouring property, there is a real argument for it. It is the biggest opening in the building, nothing overlooks it, and the material offers no resistance at all once the mechanism has been defeated. That combination is unusual enough to justify spending on that specific opening.

It covers the approach and does nothing about the door itself. A perimeter reduces casual access from outside and has no view on the contractors, gardeners and visitors who come through legitimately every day. Since a terrace elevation is the largest and least resistant opening in the house, it is worth locking properly regardless of what the gate is doing.

It is worth doing. This suburb was developed comparatively recently and comparatively uniformly, so the door systems along a street tend to be similar in type and similar in age. When one starts giving multipoint trouble, the others are frequently a year or two behind. Adjustment before failure costs a fraction of dealing with a door that has stopped locking.

In most cases, yes, and it matters more on these doors than on older ones. A modern entrance door is an engineered assembly rather than a slab with a lock in it, and forcing one damages an expensive component rather than a cheap one. The approach is to work the mechanism rather than the door, and to establish first whether the fault is the lock, the handle or the frame.