This exercise is used to build pressing power in the triceps and will help improve on the amount of weight that you can bench press.
Begin by laying down on a flat bench press. Next, reach up and grab the bar with a grip slightly narrower than your shoulders. Make sure to get the weight deep in your hand, so that your wrists remain strong during the movement. Remove the bar from the rack by pushing up and bring the bar out and over your head. Now, slowly lower the bar to your lower chest and make sure to keep your elbows in tight to your body. Pause slightly with the bar on your chest and then push the bar back up to the starting position. Focus on using your triceps to push the bar up and lock out your arms at the top position. Repeat this movement until you are done with your set. Then, carefully return the bar to the rack.
A spotter is useful to aid you with removing the bar from the rack along with helping you if you fail on a repetition. Whenever you are using heavy weight on an exercise with free weights, you should have a spotter.
This exercise can be done with dumbbells, but it is suggested that you use a neutral grip (palms facing each other) to further isolate the triceps.