Backward Knight moves are the most difficult to see.[/b]Backward knight moves are my single biggest blind spot, and it's a little ironic that two of my favorite Fischer games (Fischer-Ibrahimoglu, Siegen 1970, where he moves the queen's knight 7 times in the first 21 or so moves, and then trades it off, and the Korchnoi-Fischer blitz King's Indian Defense game in 1970) both involve knights moving backwards and redeploying.
Paul