During my BMT days, if one fails BMT, no vocation for the serviceman. He cannot attain any rank cos he cannot proceed to any vocation in the armed forces. He has no rank and vocation pay, only recruit pay for the next 2 years of his NS life.
He therefore become what in those days were termed as "GD Man". GD stands for General Duties. A more simplistic term would be - odd job labourer, road sweeper, cleaner. His job is daily area cleaning of the camp, toilet cleaning and all the trappings of a low life job.
Don't know whether this job vacancy is still available now, but if available, are you seriously considering taking up the post??