SHADOWBOXES are probably my favorite thing to do. That's because of the endless varieties of styles and arrangements and items that can be included. Also, each shadowbox is a new challenge for me both esthetically and practically. I need to arrange all the items in such a way as to show them off most effectivly, and at the same time they must be properly secured.
I use many ways to fasten objects in a shadowbox. Wood glue, silicone, epoxy, hot glue, PVA, weldbond, and wheat paste are the most common glues used in shadowboxes. It depends on the item as to which glue I use. Keep in mind that many things should NEVER be glued. Things of value, whether monetary, sentimental, or historical should not be glued as a rule. These things may be irreversibly harmed by the glue or the glue may bleed through.
Sometimes it may be necessary to sew an object into position. I use cotton, silk or monofiliment to do this. Sometimes a compartment must be made to hold an item in place. Sometimes a frame within the shadowbox is needed. Also there are many pre-made acrylic holders available on the market to hold things like knives, plates, guns, and coins, just to name a few.
To best determine a proper approach to your shadowbox needs, it's a good idea to bring your objects in and we can discuss your options.
I'm rarely stumped.