When the Torah describes the tefillos of Yitzchak and Rivka davening to Hashem in order to bear children, it says that each one davened in an opposite corner of the other. In Rashi’s words: זה עומד בזוית זו ומתפלל וזו עומדת בזוית זו ומתפללת. What is the significance that Chazal felt it necessary to let us know the specific location of where they davened whether in front of the wall or by the corner.

The ShulchanAruch (Orach Chaim 98) requires that when one davens he should feel like a poor and needy person knocking at the door of his benefactor.כרשים וכדלים דפקנו דלתיך. Therefore he must daven in the form of תחנונים supplication as would a beggar. We suggest that this needed posture and self image of the mispallel is hinted in the passuk (Mishlei 8,34) אשרי אדם שומע לי לשקוד על דלתותי יום יום Happy is the person who listens to me and is diligent on my doors of the BeisMedrash and Shul day to day.

To understand the words of ShlomoHamelech let us bring the history that surrounds the letter דלית based on the sefer זרע ברך (Bereishis). Chazal say that אדם called Hashem the name of אדון  Master. Another name of Hashem is שדיthe name used in creation שאמר די לעולמו. However, when he ate from the AitzHadaas the two dalets of שדי אדני were removed and went into galus and what remained only the letters of יש אני. These letters of these two names of Hashem, before and after the chait, tell the entire story. By eating from the AitzHadaas, Adam brought evil into himself which gave him the inner drive to prioritize his ego and self, the אני, making Man feel יש that he is a reality and not totally dependent on Hashem. Chavah refers to colossal loss of the two dalets when she defends herself to Hashem blaming the Nachash for her transgression.הנחש השיאני that it was the snake that brought me to the letters of יש אני removing from me the two dalets (Bereishis 3,13). If one takes the words יש אני it adds up to שמאל the left, the side of the SitrahAchara -סמאל  the angel of Aisav. It also spells לשמא to doubt and perhaps. Once Adam ate from the Tree of Knowledge he lost the clarity of emes and now the truth became blurry and it was mixed with the sheker.

The way to retrieve and redeem these two dalets is by totally subjugating oneself to Hashem’s will. This occurs when one feels he is deserving of nothing without the chesed of Hashem. Every possession he owns is Hashem’s, and he must beg from Hashem at every moment for life, sustenance parnassah etc. If he can successfully achieve such a spiritual state he will help redeem the two dalets and bring the geulah.

Both dalets are alluded to in the ShmahYisrael. The passuk ends with אחד the letter dalet, and ברוך שם כבוד מלכותו לעולם ועד  also ends with a daletAvrahamAvinu began the process of repairing the two dalets. Therefore he was the first one to call Hashem by the name אדני (Berachos 7b) my G-d. He was the first to have a Bris with Hashem with the name of  שדיsealing the bris (Bereishis 17,1 Rashi). This that AvrahamAvinu was the first to associate with אדני and שדיconveys that as the first Av of BeniYisrael he was repairing the chait of AitzHadaas. Avraham said on himself אנכי עפר ואפר (Bereishis 18,27) that he had two descriptions of negation to Hashem, of דלית  – dirt and ashes. That is why Hashem calls Avraham דודי as the Medrash says (R. Bachya Bereishis 15, 5) ברח דודי ודמה לך לצבי, זה אברהם שנקרא אוהבי (Shir Hashirim 8,14) Hashem’s beloved to Avraham was because he undertook the task to correct the two dalets. Therefore by possessing two levels of negation to Hashem he was able to start correcting the falling of AdamHarishon which was caused by Adam’s illusion that by eating from the tree he can become like Hashem והייתם כאלהים.

This concept is alluded to in the passuk mentioned above לשקוד על דלתותי to be diligent to repair the two dalets every day. One of the ways of attaining such a state of דלית  aside from reciting ShmahYisrael is with tefillahChazal in fact learn from this passuk that one should enter the shul far enough in with the length of two doors so it will not appear as if davening is a burden on him and he can’t wait to make a quick exit. Obviously if one feels that tefillah is a burden he lacks the true posture of tefillah of כדל  that he needs Hashem for every need big and small in his daily life.

By davening with a crystal clear perspective concerning one’s total dependency relationship with Hashem, tefillah can be the time when we bring back the two dalets in our life even if it be only momentarily. We begin the ShemonehEsraiwith the name of אדני which heralds in tefillah as a time period to acknowledge Hashem as his total Master. But it is also a time when we must commit in our hearts to be His loyal servant. This aspect of the relationship is the name שדיwhich was the name associated with the BrisMilah. The Sefer Chinuch writes that the mitzvah of Milah also applies to ומלתם את ערלת לבבכם (Devarim 10,16. In fact the external bris is to arouse one to fulfill the internal bris on the heart. Tefillah is the avodah of the heart to rectify and refine it to desire only Hashem בכל לבבך. Tefillah is therefore the avodah of reconstructing the two dalets and being mesakain the chait of the AitzHadaas.
Davening in a corner is not just a hideout away from everyone with your back towards them. Even in front of a wall can do the trick. The esoteric meaning of a corner is when two walls meet at a corner their shape is like the letter ד. It is this physical surrounding of the letter ד which can subliminally arouse within one feelings of דל and how he must subjugate his will to that of Hashem’s for without Hashem he has absolutely nothing at all. This self perception is the key to tefillah.
The Avos’s task was to fix and repair the chait of the AitzHadaas. Their future son who was to be born to them was the tikkun of AdamHarishon as Chazalsay (Baba Metziah 84) שופריה דיעקב כשופריה דאדם the countenance of Yaakov was the same countenance of Adam. That is why Yaakov’s middah of אמת adds up to (with the three letters) דלית. Yaakov when he would achieve the tikkun to the chait of Adam, then both dalets would be returned and function fully in their original positions. Therefore Yitzchak’s and Rivka’s tefillos to Hashem to merit them with a Yaakov was in the form of two זויות corners to arouse above the merit of bringing the geulahshelaimah in the form of the twodalets. Note that the gematriah of זוית  with the word is משיח בן דוד . The Moshiach will bring about the full redemption of the two dalets one for שדי and the other for .אדני
Now we can understand why DovidHamelech’s name  is spelled with two dalets. His and his dynasty’s mission is to bring the geulah and the two daletsto their former positions. It is this embodiment of the two dalets and his unusual degree of subjugation to Hashem (Dovid killed his yetzerharah) that he also embodied tefillah as he said on himself ואני תפלה . Tefillah starts with אדני שפתי תפתח a passuk from Tehillim authored by Dovid Hamelech. The ShemonehEsrai ends with the letter ם. If one looks closely at the ם he will find that its structure is made from two dalets, one on top and one upside down – two corners. The purpose of the ShemonehEsrai is to attain a clarity even if for a moment for every person to call Hashem אדני My master with a complete negation to His will. זוית contains the word זיו which means radiance of light. The tachlis of life is ליהנות מזיו שכינתו  to delight from Hashem’s rays. If we have a tefillah that possess the characteristic of a זוית  even if we are not davening in the corner, then we will merit to be newly inspired with the Shechinah infusing us with a closeness to Hashem 

– Rav Brazil
Gut Shabbos