This is today's bit of advice from the book Safety Toolbox.
The hidden ball safety type is considered by many players to be the only real defensive shot. To the intelligent player, it is simply another way to create additional problems for an opponent. Regardless of how simple or difficult the kick or jump might be; it forces an opponent to stop and think.
Interruption of his game flow is what is more important. You want an opponent to constantly be figuring out problems. A simple hidden ball setup may be easy to shoot for a legal shot. If he is careless in his analysis, it exposes a weakness in his thinking. He does not consider the consequences of a difficult shot and the result is to your benefit.
If given a difficult multi-rail kick problem, and he spends time calculating the necessary pattern, he is careful. But it also burns up a lot of brain energy and interrupts game flow. There is a cumulative effect. The indicator is when he takes longer or short shooting times to make decisions.
Do not expect ball in hand as a reward. Doing so sets up unrealistic assumptions. Expect that he will make a legal hit. All you want to give him is a problem shot that makes his life a little tougher. If you can do that, your setup was successful.
On a legal hit, billiard god luck (chaos) enters the game. It is impossible to have precise ball control when shooting into a rail first. The balls can go anywhere. Hidden ball safeties add a greater amount of chaos to the game.
At the beginning of a game, there are many balls to hide behind. At the mid-game, available shadow zones become fewer and require more skill to set up. In the end-game, hidden ball safeties are rare and difficult, if possible at all.
An excellent opponent can kick or jump to make a legal hit and often pick out which side of the target ball to hit. This could result in a return safety, usually a bad angle or distance situation. Even so, chaos still plays a role with its 50/50 results.
Available variations depend on experience and imagination. Many hidden ball safety opportunities are obvious. Other situations may require moving a ball one or more cushions to get position. The secret is practicing the exercises in cue ball speed, spin, angle, and energy transfers. Add some imagination for greater flexibility.