When I've eaten the fantastic food (well, most of the time it's fantastic) out of my canning jars and washed them out, it's time to store them until I need to can something else. I like to wash the used lid and ring along with the jar and then put the clean lid UPSIDE DOWN on the top of the clean jar and screw it on tight with the ring. The reason I don't put the lid on right side up is that the gummy stuff sometimes sticks to the rim of the jar and then when I'm ready to use that jar I have to scrape crusty gummy ick off the rim before I can use it. Upside down, I don't get any of that. I'll let you just look at the pictures to see why you want to store your jars with lids on. On the left, a jar just stored in a box, on the right a jar stored in a box with the lid on it. The lid keeps the jar nice and clean. Of course you'll still want to wash it before canning something new in it, but wouldn't you rather start with a mostly clean jar than one that's all dirty? Sometimes it's even better than just dirty ick--you'll get dead spiders/bugs in them as well--super gross! So it's worth it to save the used lid and keep it on the jar until you're ready to use it again.