Jabots are the fabric panels that cascade down each side of the window in pleats.
The jabots are mounted over a center swag on a narrow board cut to the width of the window, which is mounted above the window. To make a pattern for the swag, cut a piece of muslin in a trapezoidal shape. The bottom of the muslin pattern may be cut straight or curved. The length of the fabric may change, but start with a piece this long and go from there. Use pushpins to pin the top of the fabric to a cutting board or ironing board.