If you have a bass with Fender 60s style truss rod nut access—ie a nut with a cross-shaped slot at the neck heel, eg a JMJ Mustang, the absolute best truss rod tool is this StewMac one: https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-truss-rods/truss-rod-crank-for-tele I bought a second one from a UK seller on ebay recently to keep safe in case I lose my first one.