caranthir:
@tyrion_I Please count the number of columns again. Due to convention, there is no column 'I' (I assume, it could be easy to confuse visually with 'J'). That said, this and many other tsumego would be valid on unorthodox-sized boards too.

tyrion_l:
This goban also has 20 columns. Looks like all full size goban are oversize.