The PetPeek™ window can easily make that possible.

The PetPeek™ window is a durable, clear, hard acrylic dome 9.5 inches in diameter, with a black trim-ring and all necessary hardware for easy do-it-yourself installation into your wooden fence. It is an attractive addition to your fence.

Dogs are curious, they want to know what’s happening out there!
Help satisfy their curiosity and make it possible for them to have a peek.
More info : http://www.petpeek.info/