Lay down the cold frame end on the plastic sheeting and cut out the end piece to attach. Be sure to leave at least 6 inches overlap. Allow for corners to be cut out in an L and pleat curve side. Only cut pleats about half way into the sheeting. Do not cut all the way down to the pipe line.
See pattern below.
The black is the assembled pipe
The blue is the outline pattern for the plastic sheeting
The green is where to cut the L corners
The red is the pleating. More can be made if needed.