Sake bottle shape
makes the sake bottle shape, a knight's move from two stones one space apart.
If does not point to the center, or other stones are in contact with these three, then the shape is not the sake bottle shape. The shape is also known as dog's neck, dog's head, or dog's face.
One proverb claims "the sake bottle shape is overconcentrated" [1]. Indeed, there are many cases where b would be better shape, or the jump one space further to a (horse head) would be preferable. However, it remains a flexible shape seen in pro games. See sake bottle shape, textbook example for more discussion. According to John F., negative overtones of the sake bottle shape may involve a pun based on another word tokkuri, meaning careful, serious, plodding.
See also knight's loincloth and cutting sake bottle shape.
[1] トックリ形はコリ形なり (tokkuri-gata wa korigatachi nari)