Buttons are added to upholstery projects to stabilise the fabric and to add visual interest. While buttons can be added at almost any location on a piece of furniture, the use of two buttons is usually limited to floor pillows, and couch or chair cushions. By using double buttons on, say, a couch cushion, it can be reversed for longer wear, as each side is identical. The buttons can be sewn to float on top of the fabric, or pulled tighter to create an indented, pleated shape. While it is possible to use any type of button, those most commonly used have a single shank on the back. Use fabric covered buttons, matched or coordinated to the cushion fabric. You can purchase fabric covered buttons, or make your own with a purchased self cover button kit.
Determine where the buttons will be placed on your cushion. If you are making a floor pillow and just want one in the middle, measure from each top corner diagonally. Where the lines intersect will be the midpoint of your cushion. Mark your button location with fabric marker on both sides of the cushion.
Thread your long needle with a length of sturdy cord. Pull the ends even so you have a double cord. Be sure your double cord is long enough to reach through the cushion twice with a few inches to spare.
Tie the first button to the cord ends. Push the needle through the cushion at your marked point until the button rests on the surface of the fabric and the needle comes through the other side of the cushion, where you have marked it.
Run the needle and cord through the shank of the second, matching button, and run the needle back up through the cushion--beginning on the mark where your needle just came through and coming out just under the first button. Pull up the thread so the second button is secure. If you wish for a "deep button" look, pull the cord until the buttons reach the desired depth. Run the thread through the shank of the first button and tie it off securely, clipping the threads and tucking them out of sight beneath the button.
Find self cover buttons at most fabric and craft shops. Find long upholstery needles, as much as 25 or 30 cm (10 or 12 inches) long, through upholstery suppliers.