Using your pen tool start at the bottom and make a point, then holding your shift key down move up and make another point, then move up and over to make the point for one of the tops of your "Y" and then move to either the right or left to make the top point. Using your add point tool add a point to the top line then drag just that point and snap it to the second point you made. You will have an overlapping line but that shoudn't be visible. Adjust your top points to even them out, using the grid should be helpful with this procedure.
Thats the only way I can think of...
Tony Perkins