If my thread spool doesn't have a slot, I make one with something sharp pressed into the side of an end. It's the bobbins that drive me nuts and I love the aquarium tubing fix. I bought a tackle box and keep spool and bobbin together in sections because I was having trouble matching the exact shade of ecru, ivory and white or grey, greyer or greyish threads off the spool with the started bobbins. Now if they're in a little section together, they belong together. I can also change the section sizes and if I have multiple spools the same colour they stay together with a bobbin.