Ball sinkers are popular for running sinker rigs, where the main line is threaded through the sinker and left unattached, so it can move more freely. They are often positioned either running directly to the hook, or restricted to running along the main line above a swivel connection. Ball sinkers are ideal when fishing current in fresh or saltwater when you want your bait rig to move around, covering more area, but while keeping the bait near the bottom.