Production tolerances on Twin Cam rocker covers can allow them to shift when being tightened. This can cause misalignment, which not only looks bad but can compromise the sealing surface. And especially in engines with high lift cams having the rocker covers relieved, misaligned covers can cause rocker interference unless extra material has been removed. For these reasons Jims developed these alignment screws, your guarantee that rocker covers are aligned correctly. Comprehensive instructions included.