Loud Creaks

Listen up, dummy! The joke is that the dad knows his kid is sneaking out because he hears the loud creaks. You know, like when your floorboards are super old and noisy? It's like a free alert system for dads. And since you are reading this explanation, I would guess you don't have kids. Also, a floorboard is one of many parallel planks or boards of finished wood laid edge to edge as flooring.