a support column; and

a plurality of wafer-engagement-shelves extending substantially perpendicularly to the support column from a first side of the support column,

wherein each wafer-engagement-shelf defines a plurality of through-holes extending between a base surface and an opposite wafer-engagement surface of the wafer-engagement shelf, wherein the plurality of through-holes serve as discharge ports for a plurality of loose particulates on the wafer-engagement-shelf to exit therefrom via the discharge ports,

wherein the support column further defines a plurality of drain holes extending between the first side and an opposite second side of the support column for a fluid on the wafer-engagement-shelves to drain away therefrom via the plurality of drain holes.