(This is today's bit of advice from the book Safety Toolbox.)
When a shot is at the edges of your comfort/chaos zone, the chances of being successful may be less acceptable. For example, if you can only make the shot 40% of the time and it is a critical situation, that chance of missing may be more than you are willing to allow.
Enter the two-way shot. Playing this shot requires careful cue ball control. You plan for two possible outcomes. One outcome is for success. You pocket the ball and move the cue ball into position for the next ball in your playing pattern. And the game proceeds from there. (Also see Bank into a safety, page 103.) The other outcome is the unthinkable – you do not pocket the ball. Rather than leaving the table layout to the whims of the billiard gods, plan on both success and failure.
Making a plan for success and another for failure means you must calculate three possible results. The first is for success. The ball goes into the pocket and the cue ball goes into position for the next shot. The other two have to consider the cue ball and object ball positions for missing on the right side of the pocket and missing on the left side of the pocket.
Where does the cue ball stop in all three circumstances? There will be some guesstimating. Is there a compromise location that will be good if you succeed and protect you if you fail? If there is, that is your two-way shot. You are covered all possibilities. If there is no compromise location, default the shot to a defensive effort.
Many players cannot consider the dangers of missing – and they certainly don't plan on failure and its consequences. Their mindset is focused on offensive choices every time they are at the table. Even if they attempt to use a two-way, their lack of precision cue ball control betrays their efforts.
This shot can be made to appear an offensive effort, but is really a disguised safety. For example, you intentionally aim to the left side of the pocket, planning cue ball and object ball positions. Missing the shot would not be unexpected when it appears difficult. And, it is not your fault that the cue ball somehow stopped in a location that makes life difficult for your opponent. (Right?)
You can go for the two-way results or use the disguised defensive approach. It is your cue ball control that makes this work. Make the decision using the percentages that are in your favor.