To provide a barrier to varmints nesting under it I poured gravel between the boards in a section defined by four posts





I added an additional four blocking members after considering the problem of varmints
You can see them here, the last row of blocks in this photo counting from the right there are 8 vertical joists.
Between the first and second, second and third, fourth and fifth and sixth and seventh
They form a barrier that seals off entry into the under deck





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