Gokyo Seimyo, Volume 3, Problem 58 / Solution

Cut and descend  

is a vital move, if black plays at , white can destroy the eye in the corner (see below). Although white can now capture the four black stones by playing at a, that does not actually prevent an eye in the corner, as black can play under the stones (see below).

is a hard move to find, as it seems to give black a living bent four shape.

Snapback threat  

is the final vital move for killing. It threatens a snapback at a, so black does not have time to play b for a second eye.

Failure

Failure  

captures four black stones, but after -, black makes an eye in the corner with the under the stones play at

Ko  

This is not good enough, as it only leads to ko. is required immediately to avoid double damezumari.

(Note: This ko is not possible in the solution to Leather Scroll Problem 84, which has an otherwise identical solution).

Black mistake at

at  

is a mistake, white destroys black's eyeshape with the throw-in of at .