Board Thread:General Discussion/@comment-5551986-20181227102057/@comment-29325824-20190319211036

Well, I don't think the "nail" (if that's even translated correctly) refers to finger- or toenails at all. Considering there is also mentions of the "chain", I think both might be related to the Soul King's version of the "Saketsu".

Regardless, even if the novel has some bad parts (and I do have some issues myself), let's not forget that nothing could be put into it if Kubo does not actually approve of it, as he does supervise it.

Also, I'm not sure if I remember correctly, but there's a lot more to Urahara being ambushed. TL;DR (spoilers) I'm pretty sure Urahara let himself be ambushed and taken because he secretly agreed on something with Yukio. Also, as he says his OP bankai is better suited for support than direct combat.