“Hoist the main” is a sailing term that’s been heard on the high seas for centuries. But now, there’s a new kind of sail being built and fitted in Germany that harnesses ocean winds to provide power and conserve fuel for modern cargo ships. According to the Environmental News Network, the new device, known as a SkySail, is basically a large, para-glider shaped kite that is tethered to a mast, and can use wind power to boost a vessel’s propulsion. About as big as a medium-sized passenger plane, the SkySail can cost up to $3 million, but by saving fuel costs of more than $1,000 per day, there may soon be a new kind of energy-saving spinnaker aloft.