From the Jul Designs website:
Made and assembled in the USA
100% Genuine leather
Pedestal Buttons are improvisational. These closures require no commitment, no sewing, and no pre-planning. Instead, they are flexible components that can transform knitted garments and accessories. To use Pedestal Buttons, unscrew the leather backing and remove the back disk from the shank. Holding the front disk (on the screw mechanism 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 screw shank on the inside of the knitwear. Screw in the backing with your fingers to secure. For semi-permanent attachment and to avoid losing screws or backings, place a tiny drop of clear nail polish in the threaded cylinder before securing. This will keep the closure in place while it's on the body but still allows you to unscrew it when you are ready for a change.
These innovative screw-in "buttons" can be used not only as substitutes for conventional buttons, they may also be used to create shaping, to attach one knitted piece to another, and to baste knitted fabric so that it stays in place semi-permanently. Be creative.