Technique: The smart hook
If you have slow moving bearings that you need to inspect without disassembling and cleaning them, the smart hook can be a good tool to use.
If you can get access to the bearing from the side you can use the sharp point of the hook to feel the bearing and roller element surfaces. Very small cracks and uneven areas will be felt as a vibration in the hook handle. The material often used to make the hook is a 2 mm piece of piano wire. Reference the Idhammar condition monitoring manual 1972.