This exercise is used to develop strengths in the chest but will also work the shoulders and triceps.
You will need to use a decline bench for this exercise; most gyms have one of these. Begin by placing your feet under the pads of the bench and slowly low back on the bench. Be careful not to hit your head on the barbell, if it is there. Now, take a grip on the bar that is comfortable, for most that will be slightly wider than shoulder width. The only way to find the right grip is to experiment with different grips, but extremely wide grips can put more tension on your shoulders. Lift the bar out of the rack and hold the bar above your chest with locked arms. Next, lower the bar down until it hits your lower chest. Pause slightly with the bar on your chest and then push the bar back to the starting position. Repeat the movement for a set number of reps and then carefully rack the weight and stand up.
A spotter should be used for this exercise and other exercise that uses free weights. There is a risk that the lifter will not be able to get the bar back to the starting position, this is where a spotter will help. Also, do not bounce the weight off your chest, lower the weight slowly and control it the entire time.