They just clip on.

Cafe Rings for Draperies.

Brass plated Steel Cafe Rings.

These rings clip onto your drapery securely. Made of steel with brass finish. Two styles.
Cafe Curtain Rings are an alternative to hanging cafe curtains or sheers from the loops or rod pockets that are more commonly sewn into the top of the fabric. Designed for all window decor. The ultimate in window treatment accessories.
Drapery Supplies
Self Pleating Tape and Hooks
Drapery Header Tape (Buckrum)
Shirring, Pencil Pleat and Smocking Tape
Drapery Lining Fabrics
Roman/Austrian Shade Supplies
Drapery Cleats
Lift Cord and Accessories
Drapery Grommets - 3/8", 3/4", 1 1/8", 1 1/2", 2" and 2 3/4"
Vertical Blinds Notions
Roller Shades
Cafe Rings
3/8" Drapery Grommets
Cafe Ring, 1'' diameter Cafe Ring, 1" diameter
 each 
One inch in diameter.

Price:   $0.35    

Cafe Ring, 1 1/4" diameter
 each 
As shown above, 1 1/4" in diameter

Price:   $0.35