My clock come to think of it has a square hole but not the four bolt holes. After thinking for a while I think it was for an interior aircraft lights like custom vans have in them. http://www.jcwhitney.com/autoparts/ItemBrowse/c-10107/s-10101/p-100000154424/mediaCode-ZX/appId-100000154424/Pr-p_CATENTRY_ID:100000154424 So you could see what you were doing when you were out in the sticks rolling up a big fat one. This is just going off of stories I've heard. LOL But someone could have drilled holes in the clock to bolt it down as you can pull mine right out. I will get you some measurements and pictures when I get home.