l be unique
to LU,
inasmuch as they can be set with both blades open, when they act as
catchpoints. The locations are a) east end of Earls Court District
station,
and b) the turnback siding beyond West Hampstead (Jubilee Line). a
photograph of the latter appears on p.150 of "Principles of London
Underground Operations" by John Glover.

These can be found at various locations, usually at the exit from
sidings and where there is no space for the standard sand drag or
arrestor. They effectively put the train "on the deck" if the points
aren't set and the train carries on (the space between the running
rails just gets wider and wider until the bogie eventually drops off!).

On the Northern Line these can be found at:
Archway siding, Finchley Central south siding and Tooting Broadway
siding
diagrams are on Tubeprune's web site at:

http://www.trainweb.org/tubeprune/no...20diagrams.htm

Roger

Haven't had time to check the diagrams for the whole combine but, in
addition to any others that I've listed, they are also found at:

Willesden Green
Roger