What prevents bullets striking a soldiers chest when he is on the trench bord (fire step)?

Soldiers on the trench board, or fire step, are typically protected from bullets by the design of the trench itself, which provides cover from enemy fire. The trench walls create a barrier that can deflect or absorb some of the impact from incoming rounds. Additionally, soldiers often wear protective gear, such as body armor, which further minimizes the risk of injury. The use of tactics, such as peeking over the edge only briefly, also helps reduce exposure to enemy fire.