I love this idea! It's a great way to keep your dog occupied while rewarding problem solving skills.
Elegant stained glass Raven grouping hangs on the wall. Made with premium art glass, heavily streaked dark grey and white and opaque black glass. Brass hangers and stand-offs hold them securely at a 1/2 to 1.5 distance from the wall. Arrange any way you like! My own original design,