When you decrease loft you are closing the club face. This is why slight pulls go farther than strait shots because you are creating less loft. When you open the club face you add loft. This is why pushes normally fall short. Think of it like a flop shot, to get height on the ball you open up the club face, adding loft. 

No pro here, but it depends on the club and shot you are hitting.

If around the green with, say, an 8 iron down to wedges. De-lofting (typically putting hands forward and the ball back in your stance) will result in a lower running shot. This is just de-lofting, but remaining square. And vice-versa for higher shots

With open vs closed it is more complicated. Most say if you close the club x degrees at the beginning of the swing, to get back to square at impact you have to open the face the same x amount of degrees, thereby adding loft. And vice-versa. Sounds a bit weird but I believe it is true. If you start closed and stay closed at impact, it's going left, loft lower, or vice-versa for open.

Hopefully someone with professional/practical knowledge will weigh in with a better explanation. I think I even confused myself on this one.

Hi Robert,

This is a great question, and one we receive quite often.

Our SureFit Tour hosel system mechanically adjusts loft and lie angle, not face angle.  A change in face angle comes from the fact that when you change loft angle you also change the ground contact point on the sole.  When you add loft the ground contact point shifts back and when the driver is soled the face angle closes (please note, the face angle only changes if you sole the driver).  The opposite happens when you decrease loft.  The ground contact point moves forward and the face opens.

On our SureFit chart we include a note that says Loft = Effective Loft with a square face at impact.  Most golfers try to point the face of the driver down their intended line, or said another way, square the face at impact.  So, if you start with a closed face angle and square the face at impact you are in fact adding loft.  Lets walk through how that happens.  If you change our SureFit Tour hosel setting to B4 you mechanically add 1.5 degrees of loft to our driver.  If you sole the driver the face can close because of the ground contact point.  Most players then take the face and square it, thus adding the 1.5 degrees of loft.

If you change the setting and do not square the face, and you end up gripping the club and hitting your shot with a closed face angle, then yes, you hit it low left.  The key to our chart is squaring the face at impact.

Hope this helps