Just in case. Plan-B. A back up, in case the first is not enough. Contingent upon, given, if, in case , in the case that, in the event, on condition, subject to, supposing, in order to avoid, so that, to prevent
You should bring some extra cash, you know, double diapers." "Grab a flashlight. Double diapers if it gets dark." "I doubt the house paint will work. Double diapers, there is plenty of spray paint in the garage." "I can take the letter to the post-office double diapers the mailman comes too early.