Everybody knows that strong patents help decide the winners and losers of business competition—which is why companies applied for roughly 600,000 of them last year (though only half that number were granted). But there’s another, little-known way for companies to acquire the patents they need: they can simply buy them.

Patent sales usually involve a smaller company buying patents from a larger one, with the transfers benefiting both buyer and seller alike. This is especially true for startups, which can use patent purchases to leverage the vast R&D resources of major technology firms.