Could you please tell me if the letter daad is in fact articulated from the posterior one third or is it two thirds of the tongue?

Question
Assalaamu alaikum wa rahmatu Allah,
May Allah reward you greatly both in this life and in the hereafter for consistently providing us with beneficial knowledge.
Could you please tell me if the letter daad is in fact articulated from the posterior one third or is it two thirds of the tongue and if it is correct to say that : "Where daad ends laam begins".
Jazakum Allahu khair.

Answer

Wa alaikum assalaam wa rahmatullahi wa barakatuh.
May Allah grant you and all those who send beneficial questions great 'ajr, as you help others receive the knowledge. 
The letter is articulated from the posterior 2/3 of the sides of the tongue and the is articulated from the anterior 1/3 portion of the sides of the tongue until the sides end at the tip of the tongue.  It is correct to say where the ends, the begins as far as the area of the sides of the tongue that produces the sound, baarak Allah feekum.  The letter has a mechanical lengthening  () in which the anterior portion of the tongue rests on gums of the front part of the roof of the mouth with no pressure on it.  There should be no sound produced from this anterior portion of the tongue when pronouncing the .

May Allah reward you greatly and give you all khair in this world and the Hereafter.