If you're implying the correct orientation is grooves down then thats nonsense. The grooves were originally designed to go up, but now they often come with ribbed one side and grooves the other to give a choice. The idea the grooves are for airflow is just internet misinformation, no doubt started by some DIY youtuber and regurgitated online for years.
Learn about different styles of timber decking and how they should be fitted. The TDCA offers advice on deck boards, deck fixings, deck design and everything to do with timber decks.
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