Anne and Joe McMahon of Wilton have begun nationwide marketing of their invention, the ButterOnce\u00ae corn buttering knife. Last summer the product was in the Village Market and was launched July 10 on The Grommet website. As a result of the ButterOnce knife, which was under development for two years, the retired couple started a product design company, J&A Designs, in 2015. Their motto is "to create and market simple household products that simplify and enhance everyday life." The product has also been sold in more than 40 states.