99. Being told to use a short iron when coming out of the rough is one thing but I think that understanding why it should be used will result in more chance of this sound advice been taken

Every player I imagine has been told at least once, that when in the rough, take nothing more powerful than a 7 iron to get out. It’s amazing how much this advice is ignored. Many players fail on two counts when it comes to a shot out of rough. First of all, they are over ambitious with their choice of a longer club because they do not realize that just a little grass behind the ball is all that is required to make it a bad lie. Secondly, the handicap player does not find it easy to accept the wayward shot into the thick grass and tries to pull off unrealistic recovery shots with too long a club to get back on track. Being told to use a short iron is one thing but I think that understanding why it should be used will result in more chance of this sound advice been taken. 

You first need to realize that the longer the club, the flatter or shallower the arc of the swing becomes through the impact area. The shorter iron however produces a more circular arc of swing resulting in a steeper approach into the ball.  It stands to reason that if your club head is down at ground level for a longer duration, you are going to encounter a lot of grass before you get to the ball which massively reduces the power and results in a duff shot. The steeper arc of swing though is going to have a far clearer approach into the ball as it descends. The result is a cleaner more predictable hit.

If you take a wedge for a recovery shot, try putting the ball slightly back in your stance as this will have the effect of de-lofting the angle of the club to make it play more like a 9 iron. You can try doing the same with a 9 iron to make it play like an 8 iron but that will be the limit. If you put a 7 iron back in your stance and make it play like a 6 iron, you risk the lower flying ball getting tangled up in the long grass immediately in front of it resulting in a duff yet again.

Another point that you must address is the line you come out on. A short iron recovery will seldom give you enough length to make the fairway if you take a line for the green. All too often, you see well struck recoveries settle down further up in the rough because the hapless player got a little greedy. Every time you hit into the rough, make it a habit to come out sensibly into the fairway from where you can focus on making a good approach into the green with optimism high for a single putt. These are sound, damage limitation tactics that will always keep you in the game.