This document provides users of DO-160G additional background information for the associated test procedures and requirements in DO-160G. The information includes rationale for requirements, guidance in applying the requirements, commentary, possible trouble shooting techniques, and lessons learned from laboratory experience. It is intended to help users understand the objective and rationale behind the requirements, and to help users develop detailed test procedures based on the general test procedures in this document. DO-357 replaces the User Guides previously included in DO-160G. DO-160G Change 1 has been published to remove all User Guides previously included in DO-160G to avoid any confusion.