I was shown this method of how to join my binding about 5 years ago and I love it. I hate trimming dog ears after stitching, and with this method, there are none to trim. This technique works with any width binding and for straight cut or bias binding.
1. Start with 2 pieces of binding that need to be joined.
2. Place them both right sides up, lined up on your cutting board.
3. Taking your ruler that has a 45° angle marked on it, line the 45° line up with the bottom of the binding strips. Adjust the ruler on the right hand side so that the ¼” marking and the 45° line meet right at the corner of the binding pieces.
5. Separate your pieces and turn the top piece so they look like this.
6. Take the right piece and place it face down on the left piece, lining up the cut edges like so:
7. Using a ¼” seam, sew them together
8. Set your seam and then press them open and
TA DA! NO DOG EARS TO TRIM!