Forced proximity puts two characters who are attracted to (or antagonistic toward) each other in a situation where they can't escape each other's company. Snowed-in cabins, shared apartments, work trips, road trips, small towns where everyone overlaps. The proximity forces interaction that neither would choose voluntarily, stripping away defenses and accelerating the emotional arc. There's nowhere to hide from what you feel when you're trapped with the person who makes you feel it.
Forced proximity is one of the most versatile and effective romance tools. It works across every subgenre and pairs beautifully with other tropes. Understanding why it works (proximity collapses emotional distance) helps you engineer situations that bring characters together organically. It's also a masterclass in using setting as a plot driver.
Rival coworkers sharing a desk-to-desk arrangement, proximity turning antagonism into unbearable attraction.
Neighboring beach houses forcing two writers into each other's lives.
Claire trapped in 18th-century Scotland with no way home, forced into Jamie's company and eventually his arms.
Write a scene where two characters who are trying to maintain emotional distance are stuck in a small space (an elevator, a tent, a delayed train car). One mundane detail, a shared blanket, an accidental touch, overhearing the other's phone call, should crack the emotional wall just a fraction. Proximity does the work.