The twolink (monkey) arm was designed and built at CRRL. The manipulator comprises machined aluminum links, brush DC motors and optical encoders. The manipulator moves on a hardboard surface by gripping the plastic pieces which are attached to the surface. A graphical interface is provided to the user. The arm was built as part of a senior design project to emulate the operation of a delivery robot designed to operate within oil storage tanks for purposes of nondestructive inspection. The twolink manipulator also serves as a testbed for understanding kinematics of robot manipulators and for testing and implementation of path-planning algorithms.