Sloped ceilings provide a challenge for curtain installations because the slope will cause conventionally hung curtains to slide downhill along the slope. If the curtain needs to be functional, it is necessary to install the curtain rod level, regardless of the slope of the ceiling. If the objective is to create a curtain wall and the curtain doesn't need to open and close, other installations are better-suited to the sloped ceiling.
Cut L-shaped corner moulding the width you want for the curtain, using a radial arm saw.
Place the moulding with one side flat on the table. This will be the ceiling side. Measure in from each end 1 inch and make a mark in the centre of the moulding. Measure between the marks and divide by a number as close to four as possible that will produce even amounts.
Measure and mark that amount along the moulding from one end to the other. Example: if the measurement between your marks was 37 inches and you divided that by four, the result is 9.25. If you divided by 4.1 your result is 9.02. If you measure slightly over 4 inches, you will have nine approximately equally spaced marks.
Screw an eye hook into each mark and face all of your hooks away from the upright wood. Count your eye hooks.
Move a stud finder along the ceiling in the area where you want to mount the curtain. If the ceiling joist is positioned in the same direction as the curtain, use wall anchors to secure the moulding to the ceiling. Use a heavy anchor designed for the type of ceiling material in your home. Position a hanger every 8 inches. Screw the moulding to the ceiling at the anchors, using wood screws and a screwdriver. The trim portion of the moulding should face into the room so that the screw hooks are hidden.
Measure the height from the screw hook that is at the highest point to the floor. Measure the height from the lowest screw hook to the floor. Select a curtain panel that is taller than your tallest height measurement.
Place the curtain face down on the floor. Measure your tallest height measurement along the tall side of the curtain. Fold the top of the curtain to the inside and add 1 inch and pin. Go to the other side and measure your shortest height measurement along the short side. Fold the top of the curtain along the angle from the tall to short and add 1 inch and pin all along the top. Sew an angled header along the top of your curtain, following the design of the existing header. Hold the curtain up to the ceiling for a test fit.
Measure 2 inches inside each end of your new angled header and mark the back of the curtain 1/2 inch from the top angled edge. Divide the distance between your marks by the number of eye hooks between your end hooks and mark. Sew button holes at each mark. Hang your curtain by hooking the button holes over the eye hooks.
Keep your fabric light if your moulding doesn't screw into a joist as fabric can be heavy in long panels.