Lateral movement at the top of the pilasters. A cubicle door swinging, a user leaning on a panel and someone pushing a door shut all apply horizontal force well above the floor anchor.

Without a tie at the top, each pilaster resists that alone as a cantilever, and all of that bending arrives at the floor fixing and the panel foot. With a headrail, the run shares the load across every upright and back to the end walls.

That is why the same panel and the same anchor behave quite differently in braced and unbraced systems, and why the two are not simply a styling choice.

Because a continuous horizontal rail at head height is a ligature point. In secure mental health, custodial and certain care environments that risk outweighs the structural convenience.

Those layouts use floor-anchored or floor-to-ceiling systems with heavier pilasters, larger floor anchors and often thicker panels, because the bracing the headrail was providing has to come from somewhere.

Where a rail is retained, anti-ligature profiles with a steeply sloped top are used so nothing can be looped over and held. That profile is the reason those headrails look different from a standard flat-topped section.

The top surface. A standard headrail is usually a flat or gently curved section that a cord, a bag strap or a hand can rest on; an anti-grip profile presents a sharp slope or a ridge so nothing stays put.

The slope angle is the functional part. Too shallow and the profile is decorative rather than effective, which is why these sections are specified by their stated anti-ligature performance rather than by appearance.

Section stiffness has to be maintained at the same time, since the rail is still the brace. Anti-grip profiles are typically deeper than flat ones to recover the stiffness lost from the shaped top.

With internal sleeves at the joints, so the splice sits inside the section and the two lengths remain in line. An externally plated joint would interrupt the profile and, on an anti-grip section, create the ledge the profile exists to avoid.

Joints are placed over a pilaster wherever possible, so the splice is supported rather than spanning. A joint in mid-span is the weakest point of the run.

Thermal movement is rarely an issue over washroom lengths, but a long aluminium run in a naturally ventilated building does move, and the sleeve accommodates it where a rigid connection would not.

Structure, not lining. The end brackets transfer the whole run's lateral load into the walls, so a bracket fixed into plasterboard alone will pull through eventually however many screws it has.

Where the wall is a lined stud, noggings or a plate behind the board are needed at bracket positions, and that has to be set out before the lining goes up. On masonry, the anchor suits the substrate rather than the bracket hole size.

This is the single most common weakness found in a poorly performing cubicle run: the panels, pilasters and rail are all correct, and the end bracket is fixed into board.

It should not be assumed to. The section is sized for the lateral bracing duty, and hanging additional load from it changes both the loading and, if anything projects, the ligature profile.

Some systems offer integrated options where the manufacturer has sized the section for it, and in those cases the fixing points are provided rather than drilled on site.

Drilling a headrail on site is worth avoiding in any case. Holes in the top face of a sloped anti-grip profile defeat it, and holes in the web reduce the stiffness the rail exists to provide.

By the section profile and the bracket centres, in that order. The profile has to accept the existing pilaster tops and the existing sleeves, and profiles vary between manufacturers even where the overall dimensions look similar.

Measuring the internal dimension where the pilaster enters is more reliable than measuring the outside, because the outside carries the styling and the inside carries the fit.

Where the manufacturer cannot be established, replacing a whole run is often cheaper than adapting one length, since a mismatched splice in a structural member is not a repair worth making.