Rising to stand. As a person pushes up from a toilet or a shower seat, the hand travels up and forward along a shallow diagonal rather than straight up or straight across.

A bar set on that line lets the hand keep contact through the whole movement instead of regripping partway, which is where most instability occurs.

That is a different job from a horizontal bar, which is for steadying and pulling sideways, and from a vertical bar, which is for pulling up in one place.

It is the angle several accessibility guidance documents settle on as matching the natural rise path for most adults, and manufacturers build to it so that installations are consistent between buildings.

A user who has learned the position in one washroom then finds the bar where they expect it in another, which matters more than a few degrees of theoretical optimum.

Where guidance in a particular market specifies a different angle, the bar is chosen to that figure rather than adjusted on site.

Alongside and slightly forward of the seat, with the low end nearest the user, so the hand meets the bar at the start of the rise and follows it upward.

Mounting it reversed, with the high end nearest, defeats the purpose entirely — the hand runs off the end just as the load is greatest.

Setting-out dimensions are given in the accessibility standard that applies, and they are measured from the fixture rather than from the wall corner, which is a common installation error.

No — the two do different jobs and accessible layouts normally use both. The diagonal assists the rise; the horizontal gives a steady hold once standing.

Removing one because the other is present is a common way to make a compliant washroom non-compliant, since the schedule usually specifies each by position.

Where only one can be fitted, which bar is chosen depends on whether the user needs help rising or help staying steady, and that is a question for whoever is specifying the room.

Structure capable of taking the full load a person can put through it, which is considerable and applied at an angle rather than straight down.

The diagonal mounting means the fixings see both shear and pull-out at once, so the substrate matters more here than for a horizontal bar of the same rating.

Plasterboard alone will not do it. Noggings behind the board, or a purpose-made fixing plate, must be positioned before the plasterboard goes on, which makes this a first-fix decision.

Whatever the other bars in that washroom use, so a user's grip is consistent, and within whatever range the applicable accessibility standard sets.

Common sizes sit around 32 mm and 38 mm, and the choice is usually made once for a building rather than per fixture.

Too thick and a weak hand cannot close around it; too thin and it cuts into the palm under load. The standard range exists because both failure modes are real.

More than on a horizontal one, because the hand slides along it rather than gripping in one place, so surface friction is doing real work.

A peened or textured finish gives grip with a wet hand where a polished one becomes slippery exactly when it is needed.

Against that, textured finishes are marginally harder to clean, which is why healthcare settings sometimes accept a satin finish and rely on the bar being dried.