you might at some point need to land at a different airfield than planned - either for poor weather, taking advantage of unexpected tailwind or a passanger getting sick. The planning and PPR you did from home is out the window, and you need to resort to the standard join
Last time I had to land somewhere unplanned because of poor weather I did a straight in join, negotiated on the radio (the frequencies are terribly helpfully printed on the chart). This - talking to the airfield on the radio - was sufficiently obviously the right thing to do that I didn't bother with the fallback, which would have been to get a passenger to fish the Pooley's out of my bag. An overhead join would have been a bit of a desperate last resort.