A support adapted for use between first and second panels at a joint includes a distal end including a flange, an anchoring end including a flange and an anchor, and an intermediate section connecting the distal end and the anchoring end. The present invention also provides a process for preparing purified dialkylthiophosphinic chloride, and a process for preparing purified dialkylmonothiophosphinic acids. The rear support has a plurality of channels with a separate retainer slidably received in each channel for engaging an upper edge of a panel placed in the rack. Upon determining the confidence metric to be below a specified threshold, the user query is supplemented with contextual data.