The photo on the right shows the equipment used to measure the driving wheel axlebox guides.
The setting bar 'A' is set at the theoretical centreline of the axle using fixed datum marks on the frames to establish the correct position, fine fore and aft adjustment is achieved by moving the dolly 'B' along the threaded bar.
Once the bar is set, measurements are taken with a micrometer from both sides of the bar to the faces of the axlebox guides 'C'.
The measurements will determine how worn the guides are and how much they need to be adjusted for the axlebox to fit correctly.

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C

A

B

Copyright A.J.Morgan

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Copyright A.J.Morgan

The photo on the left shows the freshly undercoated frames with the setting bars for the axlebox guide liners in place.
Viewed looking towards the front of the locomotive, the bar for the trailing wheelset is nearest the camera, the driving (centre) wheelset bar can be seen in the middle distance with the leading wheelset bar just visible behind the ladder.