By default, most punctuation signs and some characters are designed to be combined with lowercase letters because this is the most frequent situation.

When combined with capital letters, some of them need to be adjusted to be optically aligned with the capitals. These variants are required in a good typeface so the user can access enough tools for quality micro-typography. They are called case-sensitive alternates, usually attached with the extension “.case” and accessible or activated on applications supporting OpenType features.