A hand tool is provided for the application of joint compound on wall board, having a planar blade affixed to an ergonomic handle. The blade has a concave arcuate working edge, wherein the concave arcuate curve extends the entire length of the working edge to each corner of the working edge. The concave arcuate working edge may be used to apply a self-feathered layer joint compound over drywall tape on planar butt joint or an inside corner joint. The blade is laterally flexible.