There is a widespread custom to cover one’s eyes while reciting Shema, something that is not generally done during the recitation of other parts of the prayer service. The source for this practice is a passage in the Gemara (Masechet Berachot) which tells that Rabbi Yehuda Hanasi would often be delivering a Shiur (Torah lecture) when the time for Shema came. At that point, the Gemara relates, Rabbi Yehuda would place his hand over his eyes and recite Shema. He covered his eyes in order to help him concentrate intensely on the words, and not be distracted by his students. The custom thus developed to always cover one’s eyes during the recitation of Shema in order to ensure maximum concentration and focus.
According to Kabbalistic teaching, one should cover his eyes during Shema while positioning his fingers in the shape of the letters "Shin," "Dalet" and "Yod," which spell the Divine Name of "Sha-dai." This is done by bringing the three middle fingers together, to form a "Shin," and then bending the thumb to resemble a "Dalet," and bending the pinky to resemble a "Yod." One places the three middle fingers (the "Shin") on his forehead, the thumb (the "Dalet") over the right eye, and the pinky (the "Yod") over the left eye.
There is an additional reason for covering one’s eyes during the recitation of Shema. The Shema recitation serves as an expression of "Kabbalat Ol Malchut Shamayim" – our acceptance of God as the sole King and Ruler over the earth. When we look around us and see what transpires in the world, we will observe terrible misfortunes and injustices that could potentially rattle the foundations of our faith. When we see, Heaven forbid, children who take ill and die young, and righteous Sadikim who suffer while the wicked sinners prosper, we might start questioning whether the world can indeed be run by a fair, just Supreme Being. We therefore cover our eyes while reciting Shema to symbolize our decision to look beyond or ignore the unfortunate events that transpire around us. Twice a day, we close our eyes to the world’s injustices and, with wholehearted conviction and unshakable belief, proclaim our acceptance of God as Ruler over the world. Even when we see misfortunes and suffering, we nevertheless affirm our belief in the Almighty – no less than we would if we would "close our eyes" and not see these disheartening events.
Summary: There is a universally accepted custom to cover one’s eyes during the recitation of Shema to enhance concentration. The three middle fingers are placed on the forehead, the thumb is bent and placed over the right eye, and the pinky is likewise bent and placed over the left eye.
