These kits consist of two pre-cut pieces of ductboard material (1in thickness) and two 28 Gauge S-Cleats, from which you can make a Supply and Return plenum for your Blueridge Concealed Duct unit.  This kit is sized for the 12,000 BTU BM12MCD Concealed Duct Air Handler.

They come pre-cut for easy assembly.  The supply and return sides are clearly marked to form a 30" supply and an 18" return.  If your project calls for slightly different sizes, you can easily cut the material with a serrated knife to match your installation.

Once separated, fold the material on the V shaped cuts to create a box shape, and finish the seam with foil tape, mastic and duct sealant (Accessories).  Then fit the end cap piece into either end of the supply plenum and seal with tape and mastic.  This provides a 5 sided plenum to which you can attach takeoffs for flex ducting.

Follow the same procedure with the other piece to create a return.