Measure the height and width of the door to calculate the amount of fabric required. You'll need twice the width of the door plus a 1-inch hem on both sides. Add enough in length to allow for gathers at the top, and for a 2-inch hem to provide extra insulation at the bottom of the door. Add an extra 6 inches in length if you want your drape to puddle.
Measure the width of the door for the rod, adding 12 inches to each side for balance and to allow space for the drape when pulled right back. Be aware of where the rod will attach – masonry will require a different type of nail than wood, and plasterboard needs reinforcing to carry the weight of a heavy drape. Poles and Blinds, a curtain and blinds company, advises that you check that there are no cables or pipes within the drilling area and that you measure the rod's position with care.
Buy a heavy, close-weave fabric. For narrow fabrics, buy double the length and sew a seam up the middle to get the benefit of a full drape. Buy a curtain pattern if you are adding lining, and follow the recommendations for fitting the lining.
Attach the rod to the wall above the door using the correct drill, bit and nail system for the type of wall. Make sure the rings are on the rod before you do so.
Make up your drape using your pattern and following the instructions if you're using a lining. Otherwise, sew a 1-inch hem along the sides and the top of the fabric, lay the fabric flat and iron on a fabric stiffener 6 inches wide across the whole width along the top.
Pin double-row gathering tape across the width of the fabric, with the top edge 3 inches down from the top of the fabric. Tack stitch it into place and remove the pins, then machine stitch the tape to the curtain. Knot the tape's two strings together at one end, and then pull the two strings at the other end, carefully gathering the fabric evenly along the gathering tape. Knot the strings together but don't cut them in case you need to readjust.
Insert hooks along the strings in the gathering tape, with the hooks facing away from the fabric. Space them evenly, and ensure you have the same number of hooks as you have rings.
Hang the drape from the rings and let it find its weight over a day. Once the fabric has settled, you can then pin up the hem. Take the curtain down and stitch or hand-sew the hem.