Window screen frames are the structures that hold window screens in place. They can be made of various materials, such as aluminum, fiberglass, or plastic, and are designed to fit into the window opening to hold the screen in place. The frame typically has a groove or channel around the perimeter that the screen material fits into, and the screen is held in place by a series of clips or fasteners. Some window screen frames have adjustable or spring-loaded corners to allow for easy installation and removal of the screen. They are used to keep insects and other small particles out of the house while allowing air to flow through the window.