A cable tester and a crimper are the best tools to execute the task of replacing all RJ45 cables in a customer environment. A cable tester can be used to check the continuity and quality of a cable, and a crimper can be used to attach RJ45 connectors to the ends of a cable. An optical fiber tester is a tool that can be used to test fiber optic cables, which are not RJ45 cables. Scissors are not a tool for replacing cables, but for cutting them. A coaxial cable is a type of cable that has a single copper conductor at its center, which is not an RJ45 cable either. A screwdriver is not a tool for replacing cables, but for fastening or loosening screws.