A lot of people who want to retain a “like-new” finish on their outdoor deck spring for the obvious choice: a clear sealer. But many of these so-called protectants do more harm than good. First of all, because they don’t block the sun’s UV rays, the wood can actually deteriorate under the sealer. These formulas also have a tendency to peel, which leaves your deck looking like it has a bad case of sunburn. Use a linseed oil-based stain instead, which soaks into the wood and acts as a preservative.