If you’re on the water and find yourself with O-rings but no tool to put them on with, the cap off a marker will suffice. You’ll have to roll the O-ring a little farther up the bait since the cap is shallower than a wacky tool would be, but it works better than having to roll the O-ring up the whole bait. You could do that with some worms as long as they have a tail that comes to a pretty sharp point. The salt content in many baits like this will cause the bait to have tiny little tears as you roll the o-ring up the bait and leave it looking white when it hits the water. At least with a marker cap like this, you can avoid a good bit of that.