back-to-back ticket(ing) is an against-the-rules practice whereby an air ticket is issued round-trip with only one Portion to be used.
Another is then issued roundtrip, again with only one portion to be used. In effect, this amounts to using one ticket for the outbound part of a trip, and the other for the return. The normal Saturday night stay requirement is then avoided - useful only when two roundtrip tickets are LESS than the cost of a single ticket with no Saturday night stayover. Most agents will not issue such tickets, as they can be severely penalized - please DO NOT ask for them !