Abstract: An apparatus for holding a wafer cassette on a platform of a wafer processing system is described. The apparatus includes a first guiding member and a second guiding member. The first guiding member is mounted on the platform of the wafer processing system. The second guiding member is mounted on the platform of the wafer processing system at a corresponding position of the first guiding member. The first and second guiding members define an interior boundary within which the wafer cassette is secured. The interior boundary matches an outline of a lower portion of the water cassette. The first and second guiding members together guide the water cassette to be precisely loaded into the interior boundary defined by the first and second guiding members. When the wafer cassette is located in the interior boundary defined by the first and second guiding members, the first and second guiding members prevent the wafer cassette from moving horizontally on the platform.