A prototype Beam Position and Phase Monitor (BPPM) beam line device is being designed to go in the LANSCE 805-MHz linear accelerator. The concept is to install two beam line devices in locations where their measurements can be compared with older existing Delta-T loop and wire scanner measurements. The purpose for the new devices is to measure the transverse position, angular trajectory, and central beam phase and energy of the LANSCE H+ and H- beams. The mechanical design of the new devices will combine features from previous LANL designs that were built for the LANSCE Isotope Production Facility, LANSCE Switchyard project, and those done for the SNS linear accelerator. This paper will discuss the mechanical design and fabrication issues encountered during the course of developing the BPPM.