A hinge assembly is provided for a frame structure. The hinge assembly includes a first generally flat plate having an inner face, an outer face and a bolt-receiving bore therethrough. The bolt-receiving bore extending between the inner face and the outer face along a bore axis at an acute angle to the outer face. A second generally flat plate has an inner face, an outer face and a bolt-receiving bore therethrough. The bolt-receiving bore in the second plate extending between the inner face and the outer face thereof along a bore axis at an acute angle to the outer face. A pin pivotably connects the first plate to the second plate. A first lip extends from the inner face of the first plate and a second lip extends from the inner face of the second plate.