I was inspired by this - not even my kids could find any!  Then I remember the 'FH's on the road... The FH stencil on the road is augmented by a yellow curb stone, which leads to a cover under which the hydrant lives. Sometimes there is a white concrete post with a yelow H embossed on top. This is a shot of one in my neighbouhood in Cape Town, South Africa. I am keeping my eyes peeled for more versions..

Cheers,
Clive