I am new to model builder. I am trying to write a model which selects a catchment (as seen below in dark blue outline) and then merges another feature class, which have their centroid within this catchment area (selected). It would repeat this process working through all the catchment areas. I have an initial model however this uses select and selection by location tools, as seen below, and does not merge or work through the catchment areas. Any information is greatly appreciated.