Abstract: A generally planar panel-like tool is provided including opposite end edge and opposite side marginal portions and the tool includes upper and lower surfaces and a longitudinally extending rib projecting below the lower surface of a cross-sectional shape and size to be received within and moved along a groove formed in a building panel, the rib being substantially the same cross-sectional shape as the the cross-sectional shape of the groove, but of slightly smaller dimensions, whereby the rib may be used to smooth a hardenable fluent material coating within the groove.