So I just realized both canine_dildo (136 posts) & knotted_dildo (446 posts) exist. Obviously you could have a dildo with a knot that isn't otherwise canine-looking, but I would tend to think canine_dildo is being undertagged.
The confusing part is that if you can only see the base of the dildo, you can really only be sure it's a knotted_dildo even though canine_dildos are (maybe?) more common than, say, a gryphon or dragon or something that just happens to have a knot.
But on the other hand there's no tag for images like post #949036, where there's definitely a medial_ring, but who knows, maybe it's not an equine_dildo at all??? I don't object to tagging those images with equine_dildo, but then should images like post #945999 be tagged with canine_dildo? Is it alright to assume it's canine when you can't see the whole thing? I'd think people would be more likely to search for canine_dildo than for knotted_dildo if they want to see images like #945999, at least if canine_dildo were tagged as often as it could be. But in the strictest interpretation of Tag What You See, it shouldn't have the canine_dildo tag.
Updated by Chessax