Refers to reptile scales that have a ridge down the center and instead of being smooth are rough to the touch. Snakes with keeled scales do not have a reflective appearance like those that have smooth scales. Keeled scales are uniform in pattern across all scales on an animal where they occur. Some snakes, such as the Saw-Scaled Vipers are known for rubbing their together to produce a hissing sound because of their keeled scales.