When working through a cross band repeater, either the two sides are using different bands or both sides are using two bands at once. At the same time, most if not all logging software (as well as most QSL card layouts) seem to assume that only one band is in use for any given QSO. Despite this, such QSOs must be logged (and QSL cards sent) all the time by satellite enthusiasts and users of terrestrial cross band repeaters.
So, what is the "right" or customary way to log a crossband contact? What does one write in the band field? Does anything need to be written in other fields? Should "cis" contacts (where both parties transmit on, say, VHF and listen on UHF) be logged differently from "trans" contacts (where one party uses only VHF and the other only UHF)?