Abstract: A hinge strip for a dual wall accordion folding door in the form of a continuous strip of resilient, flexible plastic material, or the like, defining a seal and hinge connecting the edge of four panels together thereby defining the interior hinge for the dual wall accordion folding door. The strip includes a central body adapted to be supported from an overhead track and four flanges projecting from the central body and connected with the panel edges. The central body and flanges may be of many shapes and configurations with a basic form of the strip including a solid central body and equally spaced identical flanges radiating therefrom. Another form of the strip includes a hollow central body and certain of the flanges being interconnected by a flexible web to define a pair of hollow interior areas to retain acoustical isolation of the panels from each other and one wall of the door from the other while at the same time stabilizing and controlling the hinge axes of the panels.