We had a great time with this project!

We made a shadow box for this signed electric guitar.  

For this shadow box, we made custom made archival wooden mounts to hold the guitar safely in place.  These mounts are screwed into box itself.

Here is a close up of the mount underneath the guitar.

Here is the mount at the top:

The mounts work with the guitar strap buttons to hold the guitar in place.

Here you can see the screws holding the mounts from inside the back of the shadow box:

To add a finishing touch to the custom box we built, matching the depth to the size of the guitar, we added a stacked frame.  

Here you see the final product in our work area, behind the scenes.  And yes, that is our vacuum cleaner making a special appearance - but it actually does help give you the scale of this shadow box, so we left it in for reference.