Kanbun

Block from U+3190 to U+319F. This block was introduced in Unicode version 1.1 (1993). It contains 16 codepoints.

The Wikipedia provides the following information on block Kanbun:

Kanbun is a Unicode block containing annotation characters used in Japanese copies (kanbun) of Classical Chinese texts, to indicate reading order.

Chart at Unicode.org (PDF)
Block at Decode Unicode

1. Ideographic Annotation Linking Mark
2. Ideographic Annotation Reverse Mark
3. Ideographic Annotation One Mark
4. Ideographic Annotation Two Mark
5. Ideographic Annotation Three Mark
6. Ideographic Annotation Four Mark
7. Ideographic Annotation Top Mark
8. Ideographic Annotation Middle Mark
9. Ideographic Annotation Bottom Mark
10. Ideographic Annotation First Mark
11. Ideographic Annotation Second Mark
12. Ideographic Annotation Third Mark
13. Ideographic Annotation Fourth Mark
14. Ideographic Annotation Heaven Mark
15. Ideographic Annotation Earth Mark
16. Ideographic Annotation Man Mark