Hard sign
The hard sign (Ъ, ъ, ꚜ) is a letter and punctuation mark from the Cyrillic alphabet. It is used in Bulgarian, Russian, Kazakh and Rusyn. It is named "the tvyordyy znak" or simply "tvyordyy" in Russian.
In Ukrainian and Belarusian, it is replaced by the apostrophe (').
Hard Sign Media
Hard sign, from Alexandre Benois' 1904 alphabet book. It shows dub′ (oak), vjezd′ (entry) and syr′ (cheese).