Combining Half Marks
Block from U+FE20 to U+FE2F. This block was introduced in Unicode version 1.1 (1993). It contains 16 codepoints.
The Wikipedia provides the following information on block Combining Half Marks:
Combining Half Marks is a Unicode block containing diacritical combining characters for spanning multiple characters.
Chart at Unicode.org (PDF)
Block at Decode Unicode

Combining Ligature Left HalfGlyph for U+FE20 
Combining Ligature Right HalfGlyph for U+FE21 
Combining Double Tilde Left HalfGlyph for U+FE22 
Combining Double Tilde Right HalfGlyph for U+FE23 
Combining Macron Left HalfGlyph for U+FE24 
Combining Macron Right HalfGlyph for U+FE25 
Combining Conjoining MacronGlyph for U+FE26 
Combining Ligature Left Half BelowGlyph for U+FE27 
Combining Ligature Right Half BelowGlyph for U+FE28 
Combining Tilde Left Half BelowGlyph for U+FE29 
Combining Tilde Right Half BelowGlyph for U+FE2A 
Combining Macron Left Half BelowGlyph for U+FE2B 
Combining Macron Right Half BelowGlyph for U+FE2C 
Combining Conjoining Macron BelowGlyph for U+FE2D 
Combining Cyrillic Titlo Left HalfGlyph for U+FE2E 
Combining Cyrillic Titlo Right HalfGlyph for U+FE2F