eThis goes on either side of th door to keep heat or cool in Summer in and the Heat or cold out. Measure the width of the door and add enough for seam allowances. my door is 36 inches. you want 4 to 5 inches on each side of door. You need to stuff with like Dillonsor Walmart Bags pack tight it takes about 100 bags on each side. I use my cane to pack them tight, then I stitch the open edge shut and it takes only about 20 Minutes to make. Hint you have to leave enough room for the door to open and close. I hope that you enjoy them.