In Liverpool, one of these blood-sports was for two lads to climb onto opposite back-garden walls (about 8 to ten foot high) in an alley, (we called them back-entries or jiggers, in Manchester they called them ginnels) and race along the top of them to see who would finish first and get the furthest.
It was popular until the posher people started to build sheds and garages into the walls, buggering up the line of our race-tracks.
Jim Carroll