Dry cavers were using directional markers long before there were any cave divers. The early cave divers in Florida saw the benefit of these markers, and Lewis Holzendorf came up with the idea of folding a triangle of tape around the line to form an arrow. These tape arrows were called "Dorf" markers, in Lewis' honor.
There were a couple of problems with tape arrows, however - they slid along the line and were difficult to feel in a silt-out. Cave Diving pioneer Sheck Exley asked fellow diver Forrest Wilson to lead a discussion group at a NSS workshop, to come up with an idea for a better arrow. Several ideas were tossed around. Eventually Forrest came up with the current design and hand-made several hundred. Forrest's arrows were sold through the Branford Dive Center in North Florida. They soon became very popular and Steve Hudson of PMI cave Rope Company asked Forrest's permission to mass produce arrows for Dive Rite.
Today, cave and wreck penetration divers from all around the world use line arrows to mark the direction of the closest exit. Markers attach easily to line and are made of corrosion proof material. Line arrows are available in yellow, white, blue, and red.