A notcher is a surrounded group of stones on the side, consisting of stones on the third line, flanked by stones on the second line.
Example of a notcher. If it weren't for the "notch" at the circled point and the marked stones, all Black stones would be on the second line.
Notchers are frequently encountered in life and death situations at the side of the board.
The term notcher is a term borrowed from James Davies' excellent book titled Life and Death.
The discussion of the life and death status of notchers and their classification have been separated into
There is also a table of notchers, showing critical notchers, i.e., notchers whose status would change if their shape slightly alters.
On all these pages you will find a code name for each particular notcher. See notcher code for an explanation.
We will also make use of abbreviations of the life and death status. See life and death status abbreviations.