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A yellow plate marked H with two numbers.
Also known as: Hydrant plate, H plate, Fire hydrant indicator, Yellow plate with an H
A British hydrant plate carries an H with two figures: the upper is the main's diameter in millimetres and the lower is the distance in metres from the plate to the hydrant. It exists because a hydrant is under a cover in the road and cannot be seen.
Denotes the location of an underground fire hydrant, mounted on a post or wall near it.
Contexts: Maps
Carries two figures: the diameter of the water main above and the distance from the plate to the hydrant below, in millimetres and metres respectively in the British pattern.
Contexts: Maps
Exists because the hydrant itself is beneath a road cover and invisible, so the plate is the only thing a crew can see from a distance.
Contexts: Maps
Differs between countries: many use above-ground pillar hydrants needing no plate at all, so the marker is characteristic of underground-hydrant systems.
Contexts: Maps
A small rectangular yellow plate bearing a large black letter H with a numeral above it and another below, mounted on a short post or wall.