Implying that there is a list of boxes that can be checked in life, indicating the various experiences
one has had, and checking off one of them. Almost exclusively in reference to sexual experiences.
One's sexual resume. Various skin colors, sexual orientations, and physical features are all examples of boxes that can be checked off
one's list.
I don't know if I'd do her (the shaved bald, heavily pierced, 200 lb woman across the way), but if you want to check that
box, go right ahead.
Man, I'd really like to check that
box (referring to the slim Asian
hottie friend-of-a-friend).