When mooring lines are tied to pilings, the lines have a disconcerting tendency to bind on the piling and prevent the boat from rising or falling with the tide. Tideminders are floating, baseball-sized spheres, like giant beads, that thread onto the loop around the piling, and work like rollers on a conveyor belt. During tide changes, Tideminders allow the mooring line to glide over barnacles, seaweed and divots in the piling, preventing an embarrasing and damaging hangup. One kit of nine balls costs $49.99. So, Tideminders are a cheap insurance policy against your boat starring in a humiliating YouTube video.