...when my sandwich goes from being three distinct layers to being a quilt.
It's practically magical for me to feel that floppy trio of layers take on that newly quilted feeling. It's the feeling that I look forward to the most. There's nothing like feeling the bite of the rotary blade into a bright, new fabric, but nothing tops the effect of stitching top, batting, and backing together.
Almost as good is that satisfying little 'clink' of the safety pins hitting the bottom of the bowl. It's the sound of progress.