Is this siding or flooring material? It looks similar to the 1x6 T&G siding I got samples of. The groove I thought was only on siding and not decking/flooring. How has it been working as flooring--no dust/dirt accumulation in the groove? no splinters or anything to catch your foot on?

It is 1x6 T&G flooring. We ended up doing "groove side up" because the top faces were in much better condition than the bottom. No splinters so far at all. There are some larger gaps in the grooves now caused by expansion/settling but we plan to re-seal them with either more urethane or perhaps some caulk. If we had to do this again we probably would have put the groove side down and done the necessary legwork to clean and prep the undersides to serve as our actual floor.