Mechanical – Knowledge of machines and tools, including their designs, uses, repair, and maintenance.
Transportation – Knowledge of principles and methods for moving people or goods by air, rail, sea, or road, including the relative costs and benefits.
Customer and Personal Service – Knowledge of principles and processes for providing customer and personal services. This includes customer needs assessment, meeting quality standards for services, and evaluation of customer satisfaction.
Public Safety and Security – Knowledge of relevant equipment, policies, procedures, and strategies to promote effective local, state, or national security operations for the protection of people, data, property, and institutions. 
