If you use LibreOffice Writer frequently, you probably have learnt to rely on the rule to manage the margins and tabs of your documents. If you need to have a different sets of units, such as Centimetres or points, you can change the unit of LibreOffice ruler.
LibreOffice is a free and open-source office suite. It was forked in 2010 from OpenOffice.org, which in turn was an open-sourced version of StarOffice. The LibreOffice suite consists of different programs for word processing, spreadsheets, slideshows, diagrams and drawings, and databases.