Y axis carriage and Z axis mount .
Pic 1 back of Y axis carriage , single bearing block at top , 2 bearing blocks at bottom of carriage , limit switch is mounted to rail bolts
Pic 2 / 3 shows front of Y axis carriage with Z axis , which cannot be removed unless you remove the Z rails because of one of the ( Pic 4 ) mounting plate ( lead screw support ) bolt holes protrudes just high enough to stop the Z lead screw mount .
Pic 5 , 6 , 7 show obviously the Y axis lead screw and it's mount to the Y axis carriage and either end and their respective mounts into the bearings at either end .
Actually enjoy the RnR part of this , brings back memories of working for Diamond Canapower in Edmonton , Alberta , Canada , service center for Babcox and Wilcox soot blowers/ poppet valves and the carriages for them .