Bowl for holding a yarn / hank while knitting etc.
Put the thread through the slots between the twirls and slightly pull it sideways-up. This will hook the thread, and the yarn will not jump up from the bowl if pulling too hard or fast. The same movement in reverse will release it.
If using big, heavy yarns, you might want to make the bowl more bottom-heavy to prevent it from falling over if pulling too hard. In the pictures, a few hard disk platters were fastened to the bottom with super glue. The bottom diameter is 95mm - exactly the same as the disks platters in standard 3.5" hard drives. A simple piece of wood should do fine, though. Or scale the print to what else you have laying around.
I also made a lid (optional) that can be used to cover the yarn additionally. If printing the bowl with low infill, there is a risk of the twirls breaking if being too rough with it. The lid makes the bowl function well even without twirls. The heart-shaped top hole makes the lid easy to lift.
As a SUPER-COOL HIDDEN FEATURE, the bowl can also be used for other things than yarns; Candy, coins, rings and false teeth.
75% (less is probably fine, but that's what I used)