Most thread spools include some sort of notch or slit in the spool to keep the thread ends from unwinding all over the place, but not so for the bobbins. There’s nothing on those little spools that will keep your thread on the bobbin where it belongs. When you have a collection of threads and bobbins, it can quickly become a tangled mess. Domenica from Easy Sewing for Beginners shows how she tames the mess of tangled threads and keeps the spools and their matching bobbins together where she can find them. The materials are inexpensive and readily available. Go to her blog to see what she does.
[photo from Easy Sewing for Beginners]