Charlotte Webb wrote:
On 11/12/08, Carcharoth carcharothwp@googlemail.com wrote:
Anyone know what a riser ring is?
As far as I can see it most commonly refers to an apparatus (shaped like one of those paper crowns you get at Burger King) which is used for adjusting the angle of one's exercise bike.
Well, that's about all that shows up on the first page of a google images search, but in this context, a riser ring is the iron casing that forms the topmost part of a manhole opening. It's the ring on which the manhole cover rests. It's called a "riser" because it rises above the -- typically concrete -- underlying structure that the manhole provides access to. The riser's height is chosen to match the thickness of the asphalt/macadam roadway, so that the manhole cover ends up nice and flush with the final surface.