What is the significance of the shapes (windows?) created by the kohen during birkas cohanim? This question and the ensuant answers detail at least 3 opinions of the gesture, I would really appreciate an answer that explains the difference between the three (as far as the significance of the shapes created by each).
The reason for the 'windows' is spelled out in Midrash Tanchuma, Naso 8:
החרכים is read as 5 apertures (ה' חרכים), thus the custom of most Kohanim to place the 2 hands together, with the thumbs touching, and the two left and right fingers of each hand paired together, with the hands otherwise stretched out.
Some Sefardim follow the Zohar: The 10 fingers correspond to the 10 distinct Sefiros. Thus, no fingers should be touching.
Some, wishing to follow both of the above customs, combine the 2. Thus, fingers 1-2 and 3-4 (that most keep together) are kept very slightly apart, with a larger gap in between 3 and 4 on each hand.
(Source: Bircas Kohanim by Rabbi Ave Gold, Artscroll 1981)