Originally Posted by
RadioGirl
Thanks for all the replies. I think the suitcase is so old and with the built-in locks, there's nowhere to attach any external lock (or cable ties, etc). I can tell her not to pack liquids, etc (she can buy stuff here in Oz) or, obviously, valuables. Should be just clothes and maybe books, so I guess she'll just have to chance it.
Books may get a checked bag pulled out for a hand inspection, just as they do to carry-ons. The x-ray machines apparently can't tell a book from a block of C4 at the checkpoint, so it's entirely possible that the same is true of the machines that screen checked bags.