I once saw a group of twenty-somethings doubled up in stitches as a male member tried to leapfrog one of these posts that were originally placed on a pedestrian track to discourage bikes.
I was walking towards them as he attempted his athletic number, but didn't seem to realise that two palms placed on a small, sloped area of old wood are bound to part under the load. And they did. Ouch. The most hysterical friend? A girl who couldn't stop laughing.