The topspin volley is a very useful shot to have in your arsenal. The technique is very similar to a shoulder level topspin shot. The only difference is that you are catching the ball in the air. The time to use this shot is after you hit a powerful groundstroke that forces the opponent to hit a high defensive shot. Since you are on the baseline you will probably not have time to move forward fast enough to hit an overhead. However, you can still catch the ball about shoulder level. A regular volley would not be powerful enough but a topspin volley could help you finish the point.