Your (Chest) pectoral muscles are developed with bench presses. It's potentially dangerous, so have a spotter close by at all times. Have your spotter help you lift the bar out of the uprights and to a position directly over your chest. Lower the weight to your chest and press it back up to arms' length again. Then, after performing the required number of reps, have the spotter assist you in placing the bar back on the uprights. You can emphasize your chest more if your elbows are away from your sides (perpendicular to your torso) during the movement, and your front deltoids more if your elbows are kept close to your sides during the movement.
