Fitters use lie-angle tape to see if the sole is contacting the ground at the center. A practice-range mat can reveal the same thing with the green marks on the sole.
Generally, if the marks are toward the heel, your shots will start left of the target (for a right-hander), and your irons might be too upright. If the marks are toward the toe, the lie angle is too flat, and misses will start to the right.
According to Titleist research, a lie angle on a 7-iron that’s 2 degrees off will produce a miss that’s 20 feet wide of the target.
The misses for short irons aren’t any better.