Mandolin ToneGard™

Directly from https://www.tone-gard.com/

The Tone-Gard™ is designed to isolate the back of a mandolin (or any similar instrument) from the player’s body, producing more volume and enhancing (i.e., guarding 😀) the tone.

You can test the concept right now without a Gard. Play your instrument normally, while facing a wall about a foot or two away, allowing the sound to bounce back directly so you can hear how your instrument projects. After you are used to the sound, hold the mandolin by the neck so that the back of the instrument is a couple of inches away from your body. Now try playing some chop chords. Go back and forth, against and away from your body, and you will notice a difference. You will hear a difference just hitting one chop and letting it ring while holding against you, then away. (If you don’t hear the difference, it’s time to visit an audiologist — no kidding.)

Another benefit is guarding the back of your instrument from wear, dings, and scratches. You can and should leave the Gard on the instrument all the time, not take it on and off. It fits in almost all cases.