The Guide Gear Hide-A-Gun Concealment Air Vent [Amazon] boasts that it will "Keep your gun hidden in plain sight!" of people whose eye level is lower than 36 inches from the floor.
Guaranteed! To you, it's a secret spot to store a gun that's easily accessible to you, yet difficult for thieves to find. Wood box mounts directly inside wall; Mounts securely between 2 studs; Frame is attached to the box via ball-bearing sliding rails; Fast access to the hidden internal compartment; Inside box size: 12" x 3" x 5.75"h.