US Patent 7159361 Pet door panel insert

A pet door panel insert which has a vertically expandable panel assembly in the upper region thereof installs in a sliding glass patio door or other entity arrangement simply without complicated tools. A positionable structure in the expandable panel assembly is controllingly spaced from a stationary structure of the expandable panel assembly and is actuated upwardly to engage the upper structure of a door frame to sturdily affix the pet door panel insert within the door frame. Opposed vertically adjustable front and rear cover slide plates are frictionally engaged by the upper region of a framework to seal the expandable panel assembly against the outside environment.