This chapter contains information on some of the handtools used by an aviation mechanic. It outlines the basic knowledge required in using the most common handtools and measuring instruments used in aircraft repair work. This information, however, cannot replace sound judgment on the part of the individual. There are many times when ingenuity and resourcefulness can supplement the basic rules. A sound knowledge is required of these basic rules and of the situations in which they apply. The use of tools may vary, but good practices for safety, care, and storage of tools remain the same.