Most
household wrenches will not work on the valves of a fire
hydrant because there are no
parallel sides on the five-sided (pentagonal) valve |
All of the angles of a valve on top of
a fire hydrant are the same size. The five sides have
equal length. (The valve top is a regular pentagon.) No
five-sided figure with these characteristics can have
parallel sides.
This means that an ordinary household wrench will not
fit. This design makes opening hydrants difficult without
the special wrenches carried by firefighters. |
