To test doneness, lift a rack up with a pair of tongs, IF they bend freely in the middle and/or fall apart they are done. Try not to get them SO done they fall apart---they might be too done and dry by then, even if you have sauced and/or mopped them. Also watch how far the bones have pulled back. About 1/2 to 3/4" all the way around and generally you're good. Beats poking holes all over trying to get a temp reading. Never tried the toothpick (thought that was for cakes--LOL), but worth a shot.