Being retained as a member of staff by the user agency where you did your national service, at the end of the service year.
It is the quiet objective of most service years and it is not automatic. A public sector agency needs financial clearance to add a post, which is a real constraint and a real excuse; a private company needs only to decide.
What actually produces it is unglamorous: turning up, being given work because you asked for it, and being the obvious person to keep when a vacancy appears in month ten. The decision is usually made long before it is announced.