Official records of men who served were often a mixture of their rank and their appointment.
Some appointments were for a trade and others involved man-management.
(Royal) Army Service Corps – Ranks were driver or private
Cavalry/Yeomanry regiments – Ranks were trooper or private
Royal Artillery – Ranks were gunner or driver [never private]
Royal Engineers – Ranks were sapper, driver or pioneer [never private]
APPOINTMENTS: these included (there were many others)
lance corporal (in WW1 it was not a rank because it could be granted and taken away by the CO on a whim – rank couldn't be).
A lance corporal was a still a private but given an appointment which gave him authority over other privates.
A CSM or QMS whilst still a sergeant would be given authority over a plain and simple sergeant
An “acting” rank was also an appointment. So, an “acting sergeant” was technically ranked a corporal (but with extra authority).
In today’s army lance corporal is a rank rather than an appointment.