Single sourcing is more than mechanical document conversion. It is an information development strategy. Although it is often confused with the process of converting paper-based documents into online formats, single sourcing is a writing strategy that enables technical writers to develop centralized information modules, then map them to distinct audiences and media. For technical writers, single sourcing means modular writing and information mapping. Rather than developing information for a given format, such as a user guide or online help, technical writers develop information modules at the element (section, paragraph, and sentence) level. They then map these information modules to preselected audiences and media. This guide explains in plain language and by example how to develop single source documents. It shows technical writers how to develop standalone information modules, then map these modules to a variety of audiences and formats using proven information mapping techniques. In essence, the guide provides a flexible framework for modular technical writing that can be applied to any audience in any medium.