I went to check this out, and it definitely isn't "anchors". I'm not sure how best to tag it, though. The closest of the wiki values is ground_slots, but it's a dedicated above-ground concrete block and there's a ring for attaching bike locks, so it doesn't really match the wiki description for that value. I've changed it to ground_slots anyway, since it's at least more accurate than anchors. Here's a photo: https://commons.wikimedia.org/wiki/File:Concrete_bike_stand.jpg