One of my children's favorite books when they were little was called "Loud as a Lion". They liked knowing the simple roar of the a lion was enough to scare away enemies. It is no different with lion head door knockers. Not only are they functional, but it looks as if it is guarding its territory and fearlessly protecting the home. This New England home, with its pumpkin colored door, is in Newport, Rhode Island.
If you are looking for a lion door knocker, I was able to find a few through one of my retail affiliate sites you might want to check out while they last.