Mike's mystery object looks like either:
1) A handrail to be used in conjunction with rungs driven into the wall or footholds in the brickwork to let boatmen climb up the wall from the boats to operate the locks (In common with Marple, Bosley locks lack landings at the tails and are beasts to work single-handed) Any rungs will have been removed as being too useful by the safety police, and any brick-moulded foot / handholds will have been removed or concreted up for the same reasons, in BW's campaign to remove regional differences from the waterways (You have only to watch the "By canal in the 1950s" DVD to see what diversity we've lost. Curved balance beams on the Regents anyone...?) 2) (and less likely) An equivalent of the block - rope pegs found on Tardebigge locks, whereby the towline was taken from the horse through a pulley on the mast and forward onto a pin like an inverted "L" facing in the direction of travel, over which an eye was dropped. For the first 10-15 feet of movement out of the lock this gives a 2:1 advantage to the horse, then when inertia is overcome a toggle spliced into the line jams and the arrangement changes up into 2nd gear, As the end of the line reaches the pin it drops off (as the pin's facing the way the boat's travelling) until picked up at the next lock. You can see this in action on the Sight Seen "Towpath encounter" video. The arrangement in Mike's picture looks likely to catch an eye and stop progress, so the first option is more likely. Ray Butler nb Owl and sometime horse-boat steerer 2 [Non-text portions of this message have been removed]
