If you use a (card game organiser)[https://www.thingiverse.com/thing:3759491] for the cards that you play, you might realise that you'll need to exhaust/tap the cards from time to time whilst the organiser doesn't allow you to do so.

In such cases, you may use these tokens to keep track of which cards have been already activated during the current turn.

For games like Arkham Horror, each investigator shouldn't need more than three of them since no more than 3 actions are allowed per turn. Some investigators, however, might have extra actions per turn and anyway they might need to exhaust cards using free actions, so I would advice to print 6 of them, just to be sure. Print more if you want to use them to keep track of exhausted enemies as well.