This guide provides an introduction to stock screening, or the use of filters to determine what companies or activities to invest in. Screening is one of the most widely used tools by asset owners and fund managers in implementing a responsible investment policy. This guide highlights several reasons why investors use screening, and provides data on PRI signatories’ use of such strategies. It outlines key steps that investors follow when implementing a screen, and discusses the pros and cons of divestment and engagement. It also provides an overview of the history of the practice, from the apartheid divestment movement to contemporary moves to sell out of coal.