Insect and Spider Identification: CLOSED: What kind of bee/wasp/hornet made this?, 0 by Niere

Niere wrote:
I thought I could figure this out on my own by doing a google search but I came up empty. Can someone please tell me what kind of insect made this? At first I thought it was a mason bee but then I read that they don't make their own holes. Then I thought it was a carpenter bee but I don't think they make these kind of holes either. Anyone have any idea? The below picture is a picture of a piece of wood that was anchoring an electrical outlet that serviced an above ground pool for the previous owners of our home. When we purchased the home we had them remove the pool, but the wiring etc. is still in place. This summer I put a lasagne bed around the board, stuck a wire frame pyramidal obelisk over it and planted scarlet runner bean all around it. As you can see the insect has made a hole in the board and I'd like to know if I should leave it alone or fill it up. If it's a beneficial insect then I'm fine with leaving it, but if it's not I'd rather not let it go and get stung later on when I'm tending the beans.

Any thoughts would be appreciated. Thanks!