An interesting way of putting a question.
I would
suggest the interviewer was asking if you had ever worked in a deep strip engine overhaul bay or a component repair bay.
I say this based on the "old" R.A.F servicing terms, third line being the mobile M.U world, and fourth line being the places like Woodhall Spa, ( Tornado engines )
St.Athan ( various airframes ) and Sealand (avionics) all of which were a prison sentence if you were not inclined to work in a factory clocking in and out.
I appreciate the last part of my reply will probably mean nothing to you, but will to others on here...sorry about that, but I do feel my second paragraph probably answers your question.