How to Sew a Button on a Coat or Jacket
Start with a double-threaded needle. Bring the needle up through the wrong side of the fabric and one hole of the button.
Lay a toothpick across the button. Stitch as with light fabrics but go over the toothpick. For the last stitch, pull the needle down through one hole but not the fabric. Remove the toothpick; pull the button up.
Wind the thread around the stitches between the button and the fabric a few times, creating a shank. Poke the needle back through to the wrong side of the fabric and knot as with light fabrics.