Abstract: A non-marking sealant tool is directed to applying sealant to structural joints. A shape and material of the tool are determined to minimize marking, damaging, scratching, and the like, of softer substrate materials including glass, painted tiles, and the like. At the same time, the shape and material of the tool are determined to maximize sealant performance by providing an optimum sealant shape. The tool comprises a handle and an applicator portion. The handle is shaped for comfortable fit in a user's hand and for ease and cost of manufacturing. The applicator portion has a maximum thickness along its longitudinal axis, which decreases approximately linearly toward its edges and provides optimum edge thickness for sealant application. A tip section of the applicator portion has a spline radius with a passive or aggressive shaped curvature.