Remove the drapes from the rod. Remove the rod from the wall and lay it on a flat work surface. Place the rod so the mechanics are face up.
Measure the length of the drapery rod and pull using the tape measure. Add these two measurements together and multiply by two to determine how long the replacement cord will be. Cut a length of cord to correspond with that measurement.
Slide the carriers to the ends of the rod so that they are in the open position. Cut the knots in the cord attached to the carriers. Carefully pull out the old cord.
Insert one end of the cord through the pulleys on the drapery pull side of the rod. Slide the cord through the opening in the carrier closest to the end of the rod. Tie a knot at the end of the cord to hold it in place.
Take the other end of the cord and loop it through the pulley and pull it towards the opposite end of the rod. This creates a loop that functions as the drapery pull.
Thread the cord through the carrier and across the rod to the pulley at the other end of the rod. Pull the cord through the pulley and then around and back to the carrier where the other end of the cord is attached. Insert the cord though the opening in the carrier and tie a knot in the end of the cord to secure it.
Push the carriers together to the center of the rod and hang the rod back on the wall. Tugl the drapery pull to tighten the cord and make sure the carriers move easily across the rod.