A pair of tapering movable rails forming a junction at which railway vehicles are directed from one set of rails to another; the junction as a whole.

in court, in open court or before a tribunal [OED]

[Note 102.1] Bar571~Humble Heroes was published under the pen-name of 'Fun'

[Note 102.2] "And then we 'spose we'll have some trembling pointsman 'at the bar'" :- The poet is cynically assuming that the pointsman will be blamed for any accident resulting from poorly illuminated locomotives.