Why are checked-out reservations disappearing?

Q: Why are checked-out reservations disappearing from the Rack?

A: There is an option under Maintenance / Program Options / Reservations that has been checked.  You need to uncheck "Remove checked-out reservations from the Rack (make available for extra check-in same day)".  Now all checked-out reservations will re-appear on the Rack.

So why enable this option?  It can be useful to clear reservations from the Rack immediately, e.g. if someone checks in and then leaves the same day, then the only way to make the site "available" that day for a later check-in is to enable that option.  (If they were there overnight then you could always change the Last Night to the previous day, but that's not possible if they checked in and checked out on the same day.)