Proper Sight Alignment
Assuming your handgun is properly zeroed, sight alignment issues will show up quickly on target—as in these examples. At far left, proper sight alignment: Top of the front sight even with the top of the rear sight, front post centered in the rear notch.
Source: http://weaponsoffreenation.blogspot.com/2014/09/how-to-cure-common-shooting-mistakes.html
Hey, this shows a Springfield. Do you have a chart for Glock? 😉
Or, if you’re shooting a Steyr, you put the small triangle inside the big triangle with the tips of both where you want to hit. It’s nice!