In "The Shawshank Redemption", Andy is shown hiding the rock hammer in a bible whose pages have been carved out in the shape of the hammer. The question is: how could he have managed to do it? It would have taken him a very long time to do that, perhaps several months. Where would he hide the hammer until then? How could he get rid of the parts of the pages that he had carved out of the book?
Also, would it not have been better to hide the hammer in the tunnel itself, once the tunnel was longer/wider than the hammer? To find the hammer then, they would have to find the tunnel first. But if he hid the hammer in the bible, all the warden needed to do was to open the bible, which he didn't (thankfully!).