When both characters have had an Unresolved Sexual Tension for a long time, occasionally fate helps a little by making one of them trip for some reason (often a fight) and fall on the other. They may both lose their footing and fall to the ground, or the standing one might brace the impact against a wall. Either way, awk-ward.
In some cases, if this trope is in action, by the magic (and surprise) of their sudden proximity, they will fall silent. They'll look intensely into each other's eyes, forgetting their fight entirely.
Many fans often ship all the time (context or no). Producers, especially those who keep their finger on the pulse of the audience, not to mention their eye on the fandom, know this. So, they decide to tease these fans with hints about possible romantic entanglements, and thereby build that emotional attachment between the show and the audience as much as they can.
Oftentimes, they will find themselves gazing deeply into each other's eyes, one indication of their Unresolved Sexual Tension
Accompanied by some passion on one (or both) of the partners in the gaze, hence it fits into the passionate look variant of the trope and it is also a subtrope of Longing Look, but different in that it is two people holding each other's gazes.
When a character ships two other characters in the story, trying to make them realize their true feelings.
They might think it's cute or that the persons they ship are good for one another or they could have any number of ulterior motives for wanting people to get together (such as want to be adopted)
The shipper is usually a secondary character and the characters shipped are the protagonists of the story.
Two people are obviously attracted to each other, but some element of the story is keeping them apart. This tension is frequently referred to as unresolved sexual tension in fandom
Battle couples are getting more and more common in media. Often, in m/f pairings, the woman will often not be a conventional soldier, but a partisan of some kind.
This is the kind of couple where bullets figure prominently in the story of their romance. Where "war buddy" and "significant other" are synonyms.
Their mere presence increases the chance of a Back-to-Back Badasses scene.
A stock visual metaphor, if you will. Some people (usually a pair) are separated by a wall, window, or other barrier.
In order to make the best of this image (...) the camera will move around the set to show that they are physically very near to each other, but still incapable of touching. If the couple is lucky, they will have a small hole or window to communicate through.