Mattil created the first woodshop at Pi Beta Phi School funded through the industrialist Louis E. Voorhees of Cincinnati. Voorhees would later donate his Tennessee property and buildings for the founding of the Great Smoky Mountains National Park. At the shop students constructed cabinets, furniture, mountain furniture reproductions, miniature beds and chests. He researched, searching remote mountain homes, then reproduced traditional mountain designs in his pieces as well as creating new designs. Many of the Gatlinburg, TN woodcarvers such as Carl Huskey studied and worked under Mattil and created their own woodshops and carving businesses.
In the 1930s - 40s Mattil taught adult education at the Tennessee Valley Authority Center in Norris, TN after the TVA created the lake and electrification at Oak Ridge. Many of his students were workers on the 1933 dam construction. He worked with the Civil Conservation Corp (CCC) and with young men in thirty-four east Tennessee counties.
Mattil joined the Guild at its official founding in 1932 representing his business Woodcrafters and Carvers. He participated in the first traveling exhibition of the Guild in 1933 under the American Federation of Arts sponsorship. That show with over 500 items traveled to Washington, D.C., New York, Illinois, Nebraska, Missouri, Pennsylvania, Wisconsin, Virginia and Kentucky. Mattil served on the Guild Board over 34 years, being President from 1937 to 1940and 1966 to 1967. He was regarded as "Mr. Craftsman's Fair" by assisting with the Guild fair from its founding in 1948 and leading its organization and set-up for 43 fairs. When the TVA founded the craft organization, Southern Highlanders, Mattil participated on the Board of Directors until it joined the Guild in the 1950s. He served on the Guild's Old Crafts Committee which supported a museum of old crafts for the Great Smoky Mountains National Park resulting in the historic farm at the Oconaluftee Visitor Center. Mattil was awarded a Guild Life Membership in 1965 and was declared "Director Emeritus" of the Guild in 1971. He died in 1976. Mattil and his woodworking were mentioned several times in Allen Eaton's Handicrafts of the Southern Highlands. Mattil and his incredible volunteerism over three-quarters of the twentieth century contributed significantly to the success of crafts and craft organization in the Southern Highlands.