This curriculum guide, the fourth in a set of six, contains teacher and student materials for a unit on mechanical engineering prepared as part of a seventh- and eighth-grade agricultural science curriculum that is integrated with science instruction. The guide contains the state goals and sample learning objectives for each goal for students in grades 8-10 and a teacher presentation outline for the unit. The unit, which begins by listing the agricultural practices and science concepts to be taught, along with activities and applications, contains the following components: teaching steps, lesson outlines, teacher's presentation outlines for each day, student information guide, terms and definitions, worksheets, student activity note sheets, student activity information sheets, student activity record sheets, quizzes, practice problems, and 12 transparency masters. Teacher's activity sheets and tests have answers provided. The unit covers the following topics: (1) selection of the best horticultural or agricultural tool for a job and (2) agricultural mechanics. (KC)