A single panel design, pd small units open from left to right with precision smoothness. Even the smallest kitten or puppy can easily push open the door. All four edges of the single plexiglas panel are equipped with the same industrial grade weather stripping as the larger units and provide the same level of energy efficiency. The spring loaded 4-way lock can be set to in only, out only, in and out or locked. Simply turn the knob to set. Pd small units do not come with a security plate.