Answer: Calder & Hebble Canal. This is Salterhebble Bottom Lock with its guillotine bottom gate. John Gagg slide 542 dated July 1974.
Correctly answered by: Alan Dodds, Andrew Roger Nuttall, Andy McLaughlin, Cathy Crotty, Cyril J Wood, David Tucker, Ian Cleathero, Ivan Cane, John Healey, John Lower, Ken Nelson, Laurie Gibney, Martin Hunt, Mel Tyerman, Michael Rollin, Mike Fretwell, Mike Spick, Paul White, Peter Oates, Peter Rayner, Richard Bates, Rick & Harri Barnes, Roger Turner, Simon Judge, Stephen Traynor, Tony Clayton, Ulrich Signer.
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