These are diving planes for trolling, they help get your lure deeper without having to be further back. There are three designs, center, port, and starboard. The port and starboard units will also move your baits out away from the boat, maybe about 1 foot for every 5 back. Not like a planer board, but enough to give you a wider spread.

These are designed to float when not being pulled through the water, so if you stop the boat, your lines don't end up snagged to the bottom. Do not weight them down. You can adjust the dive rate by using different combinations of upper and lower holes.

Rigging suggestion: Attach a split ring to a lower hole. Use a small piece of steel leader, 4 to 6 inches, attach one end to the split ring, and TIE the other to the upper hole, tied on with some weaker line (4 to 6 lb test) represented here by the orange yarn. Attach your bait leader to the split ring, and your main line to the upper swivel. With this rigging, when A fish strikes, the weak line will break and you will only be fighting the fish, not the plane. This also means the strength of the plane will never be pushed beyond it's limits.