This was by far one of my favorite gifts to make! It is called a secret hollow. So not only did the recipients get a discreet hiding place, I also filled it with mock "secrets" like fake handguns and cigars. There is an easy way to make these and there is a difficult but more precise way to make these. All you need is some glue, water, a book (the thicker the better), a razor blade (or a ban saw). I made one with the razor blade my Dad caught me and cut the rest on the ban saw. It cut the time by about 2hrs... Here is the tutorial I used.