Abstract: A neat, finish quality trim joint is prepared between an upstanding dry wall partition and the ceiling to conceal a gap and ragged upper edge of the partition left during erection of the partition. An elongated, inverted, transversely L-shaped member of the joint is secured to the face of the partition along the upper marginal edge thereof in such a manner that the vertically extending leg of the member covers the gap while its other, horizontally extending leg lies up against the ceiling and projects outwardly from the partition generally into the roomspace. With the member secured in this manner, the finisher spreads a layer of mortar over the vertical leg and adjacent portions of the partition in order to provide a smooth transition from the partition to the member and to fully conceal the vertical leg. In applying the mortar, the finisher may advantageously run the edge of his trowel along and abutted against the horizontal leg which protectively masks the ceiling at this time.