Buy a hose clamp to attach to the post of your tool rest. Put the clamp (loose fit) on the post of the rest. Carefully adjust the rest so the tool is exactly at centerline of the work piece, then lower the hose clamp to contact the banjo, and tighten. Your tool rest is now automatically referenced to the correct height for turning. This is typically the lowest setting you will use, so no need to loosen the clamp when using other tools.