Abstract: A storm window or a roof or wall section of a building is formed form a plurality of double interlocking panels, each panel having left and right side strip sections of specific cross-sectional shapes that a locking force is developed between two panels when engaged at the strip sections. The locking force developed is proportional to a load applied against the panels. This increase in locking force between panels allows for the panels to be made from lighter stock material, yet still maintain the structural integrity that would normally be found in a heavier stock material.