Because ordinary drives invite interference. A cross or slotted head can be turned with a coin, a key or a nail file, and washroom hardware is unsupervised by definition.

Removing a latch or a hinge screw takes a cubicle out of service and can leave a sharp edge or a falling panel. In schools and public buildings it is a routine form of vandalism rather than a rare one.

Pin-in-head, one-way and proprietary drives raise the effort enough to deter casual tampering. They do not defeat a determined attempt, and they are chosen on that understanding.

By the recess geometry rather than the head shape. Count the lobes or points, look for a central pin, and note whether the recess is symmetrical, since one-way drives have ramped flanks that only accept torque in one direction.

Photographing the head against a scale is more reliable than describing it, because several proprietary drives look similar at a glance and take entirely different bits.

Where the drive cannot be matched, replacing every fastener in that assembly with one known type is usually better than sourcing a single odd bit that will be lost before the next service visit.

A machine thread into a metal insert or through to a nut, in preference to a coarse self-tapping thread cut into the laminate itself. Compact laminate is hard and brittle in thread form, and a cut thread strips under cycling.

Where a screw does go directly into the panel, a coarse, deep thread designed for dense boards holds far better than a wood screw profile, and pilot hole size is more critical here than in timber.

For anything carrying real load, through-bolting with a washer on the reverse face is the durable answer, since the panel is then in compression instead of relying on thread engagement.

Austenitic stainless in the 304 range is the normal minimum, and 316 is specified where chlorides are concentrated, which means pool surrounds, coastal buildings and washrooms cleaned with chlorine-releasing products.

The trap is a plated fastener that looks identical when new. A zinc-plated screw in a wet cubicle will show rust staining down the panel within a season, and the stain is often the first sign that the wrong fastener was used.

Mixing grades within one assembly is also worth avoiding. A lower-grade screw in a higher-grade bracket corrodes preferentially and can seize in the hole.

Very much. A screw that is too long protrudes through the far face of a door, which is a laceration risk at hand height and immediately visible; one that is too short engages too little thread and works loose.

On a through-bolted pair, length is set by the panel thickness plus both escutcheons, so a change of door thickness changes every fastener in the assembly.

This is the most common error when hardware is transferred between systems, because the head and drive match perfectly and only the length is wrong, which is not apparent until the part is tightened.

Once or twice, if the drive recess is undamaged and the thread is clean. The recess is what usually fails first, and a rounded recess on refitting is worse than a new screw would have cost.

Any fastener showing corrosion should be replaced rather than refitted, because the corrosion is evidence that the grade or the environment has changed and it will progress.

For security-drive fasteners specifically, replacement is the norm. The drives are shallow by design, and each removal takes a little more of the recess with it.

On laminate faces, generally yes. A washer spreads the clamping load across a wider area of a brittle surface, and without one the head can dish or craze the face as it is tightened.

Nylon or fibre washers do a second job by isolating dissimilar metals, which matters where an aluminium bracket meets a stainless screw in a chloride-rich atmosphere.

They also take up minor irregularity between a bracket and a panel face that is not perfectly true, which reduces the tendency of the fixing to loosen as the assembly settles.