On a sailing vessel, a backstay's the piece of standing rigging that runs from the mast to the transom of the boat, counteracting the forestay and jib. The backstay's an important sail trim control and has a direct effect on the shape of the mainsail and the headsail. Types of backstays There're two general categories of backstay: The permanent backstay's attached to the top of the mast. The running backstay's attached about two-thirds of the way up the mast (sometimes at multiple locations alon… (More on Backstay)