Two checkboxes acting as one

I have a question.

I have two checkboxes on a page and I want them to act as only one. For example, I select one, and the other is selected automatically, and vice-versa. I've managed to select both of them at once, but I can't seem to figure out a way to deselect them at once.

And what's bothering me the most, is that it's probably a super simple line of code that I'm simply not remembering.

Is there a way to do this?

Thank you all.