[wingnut60]

Just trying to point out that altho DRVs have an all-aluminum 'superstructure' this does not preclude that there aren't some wooden sections. And, you're right, never heard of plywood used for 'framing' but lots used for covering framing. Was being a little facetious in talking about the 'frame' of my shower skylight, but it in fact has left-to-right aluminum truss components, and front-to-rear wooden components, and to 're-frame' the skylight necessitated the use of 'wood.'
Joe