Hello,
Everybody knows that drills improve our shooting skills. No doubt. But in my case one drill also save my money. 
The story began when I transferred my Walther PPQ to my son and bought CZ P-01 Omega (I’m fan of metal / aluminum frame).
The moment I started shooting CZ I noticed it shot low (sometime it was extremely low). 
Never had this with PPQ. 
So I found solution (acually… Google found it). I had to change front sight or rear sight… Hmmm great, simple… but, unfortunately, expensive idea 
Anyway… I found the way how to calculate my front sights dimension, based on shooting results (it’s called “sight math” [I learned something 
])
I took my pistol to the range, made measurements after 100 rounds… and then RSO appeared asking what I was doing… I explained.
He grabbed my magazine, filled it with mix of live and dummy rounds and told me to shoot.
I did it 5 times (I never knew how many total round, how many live and dummies.) He took video every time so we could discuss the problem.
I COULD NOT BELIEVE THE FINAL RESULT. After 20 minutes I didn’t have to change my sights anymore 
. Money stayed in my pocket 
The drill is called " The Snap Cap Drill" (presented by USCCA)
Here are some pictures from my shooting:
BEFORE DRILL:
DURING DRILL:
AFTER DRILL:
It is still not perfect… but this is not a case here… Hopefully few more days and all hits will land in red circle. 
So as you can see, that’s the beauty of drills.
I’ve been dry firing with this pistol, using laser cartridge, and laser has hit perfectly before this drill…