From the Jul Designs website:
Made and assembled in the USA
100% Genuine leather
JUL Lisbon Ring Closure can close a sweater, shawl, cape or capelet, even shape the back of a sweater. The closure is a flexible component that can transform garments. The closure is a unique alternative to a shawl pin. It's a button for garments that don't have buttons or buttonholes. Sold per piece.
To use JUL Lisbon Ring Closure, unscrew the backing and remove the back disk from the shank. Holding the front of the closure (on the Chicago Screw shank), work the shank gently in between the stitches of your knitwear from the front. Place the back disk of leather, smooth side out, over the Chicago Screw shank on the inside of the knitwear. Screw in the backing with your fingers to secure.