Chinese Character Stroke Order - Supplementary Rules 2

Three-sided surrounding structure (三面包围结构)

16 - Gap faces upward: inside before outside (缺口朝上: 先里后外)
Examples: 击, 画

17 - Gap faces downwards: outside before inside (缺口朝下: 先外后里)
Examples: 凤, 同

18 - Gap faces rightwards: top before inside then bottom left (缺口朝右: 先上后里再左下)
Examples: 区, 匹