Lie on the bench under the fixed bar and unrack it by rotating your wrists to release the hooks, then lower it to your chest along the machine's fixed vertical path rather than the slight arc a free bar naturally travels. Position your bench so the bar lines up over your chest, not your face or stomach, before you start. Because the bar can only move straight up and down, your job shifts almost entirely to pushing hard rather than also stabilizing the bar's path. Press back up to a near lockout and re-hook the bar by rotating your wrists again when you're done. The trade is less stabilizing demand on your shoulders, but also less freedom to find the path that suits your build.