Pillbox

A Pillbox, also called an Enclosure, is a formation of stones enclosing an area of potential territory. The surrounding stones establish a boundary around the interior, but that boundary may still be subject to invasion or reduction.

Its purpose is to surround and secure territory while limiting the opponent’s access to the enclosed area. A Pillbox is a formation or territorial framework, not automatically completed territory. A larger, more open framework is generally called a moyo. The formation can also be overextended, inefficient, or vulnerable to invasion: surrounding space alone does not guarantee territory.