I came across this question on Quora a few days ago and could not resist to add to Everything Sweden. The question was:
What do these red signs found in Stockholm represent?
They don’t show minimum height of road pass for sure. I wonder if they are somehow related to fire hydrants located nearby (I haven’t seen any).
A guy called Anders answered to say that they are used to help firefighters find the nearest fire hydrant. The sign means that there is a fire hydrants 1 meter in the direction of the sign. Because fire hydrants in Sweden are hidden in walls or manhole covers, which are sometimes covered by snow, this helps firefighters get water to attack the fire quickly.
Thanks to Anders Gabrielsson and Mats Denberg for their answers.