Article: Capitalisation in English, in terms of the general orthographic rules independent of context (e.g. title vs. heading vs. text), is universally standardized for formal writing. (Informal communication, such as texting, instant messaging or a handwritten sticky note, may not bother, but that is because its users usually do not expect it to be formal.) In English, capital letters are used as the first letter of a sentence, a proper noun, or a proper adjective. There are a few pairs of words of different meanings whose only difference is capitalisation of the first letter. The names of the days of the week and the names of the months are also capitalised, as are the first-person pronoun "I" and the interjection "O" (although the latter is uncommon in modern usage, with "oh" being preferred). Other words normally start with a lower-case letter. There are, however, situations where further capitalisation may be used to give added emphasis, for example in headings and titles (see below). In some traditional forms of poetry, capitalisation has conventionally been used as a marker to indicate the beginning of a line of verse independent of any grammatical feature.

Question: What is capitalization commonly use to indicate in poetry independent of any grammatical feature?
beginning of a line of verse