Square of the pawn, a trick to save time

One technique you will often find in beginner endgame books is the 'square of the pawn' method.  It allows you to know if your king can stop a pawn from queening in time at a glance.  It is also very simple. 

Draw a diagonal line from the pawn to the edge of the board, toward the king in question.  That makes a square.  If the king can move into the square, then he can stop the pawn.  Warning!  There is an exception listed below. 

                           Black can move into the square of the pawn

            Note that this does not guarantee you will save the game, or that you can really stop the pawn.  It just lets you know that if nothing else gets in the way, you will stop the pawn.  It doesn't tell you if white can block you with his king or if his knight can get in your way, etc.  

   There is one very important exception!  In the following position, it looks like black is in the square of the pawn, however a pawn that can still make 2 moves forward actually has a smaller square!  Don't forget that - it can make knowing the 'square of the pawn' actually worse for you.  

 Please make use of this technique - it will save you lots of time!