It is for thread-thread, and fabric ravels, etc. Anything that is extra that shouldn't be there. The threads in your piecing are in the 1/4" seam allowance-that's great. But any extras that aren't trimmed, or fabric ravels are not welcome. As a for instance: you've left some longer dark threads. You have some white fabrics in your quilt top. If those longer dark threads happen to show through on the white fabric, both you and I would be concerned!
Please do trim threads, also square up the top, remove selvages, and press the top. These steps are appreciated!
