Other manhole shapes can be found, usually squares or rectangles. For example, in the United Kingdom nearly all manhole covers are square or rectangular and very occasionally triangular, but almost never circular. Nashua, New Hampshire, is unusual for having triangular manhole covers that point in the direction of the underlying flow. In 2011, the city began gradually phasing out the triangles,[9] which were made by a local foundry, because they were not large enough to meet modern safety standards and a manufacturer for larger triangles could not be found.[10] Some manhole covers in Hamilton, Bermuda, are triangular, and hinged. Some triangular water-main covers also exist in San Francisco.[11]
