What does the Pasuk mean when it writes "Veyih'yu So'amim mi'Lematah"?
Rashi: It means that the two prongs at the base of each plank must be cut in such a way that the plank will fit plush on to the socket that housed them, in such a way that all the boards formed a straight line.
Seforno: This Pasuk and the following one are referring to the rings that are to be fitted on to the two ends of the western wall 1 - corresponding to the rings on the northern and southern walls. 2
What does the Pasuk mean when it writes Veyachdav Yih'yu Samim el Rosho"?
Rashi: It means that, likewise, that the tops of the boards must form a straight line. 1
Shabbos, 98b: it means that although they were an Amah wide at the bottom, they were tapered down to finish at a finger-breadth at the top 2
Shabbos (Ibid.): Based on the Pasuk in Yehoshua, 3:16 "Tamu Nichrasu" ('finished crossing').
What are the rings mentioned here? What function did they serve?
Rashi and Ramban #1 (citing a Beraisa): Joining every two adjoining boards via a ring that fitted into two grooves that were cut into the top of the boards, one near the end of each plank, would ensure that the boards did not move, and consequently, that they all formed a straight line on top, just as they did at the bottom. 1
Ramban #2: It refers specifically to the two corner boards on the north-west and the south west 2 (mentioned in the previous Pasuk), which were joined to the north and south sides via the same method of a peg and a hole.
Seforno and Rashbam (in Pasuk 28): It refers to the rings on the outside of the boards 3 that housed the bolts that the Pasuk is about to discuss. And the Pasuk is informing us here that rings were fitted on to the northern and southern ends of the western row of boards, into which the northern and southern bolts fitted. 4
See Ramban's objections to this explanation. He partially refutes his objections, by explaining that the Torah mentions the rings as if we already knew about them, since that is how one normally fits boards together. And the same applies to the words "ve'es Tab'oseihem" in Pasuk 29 - See also Seforno there - and "ve'es Vaveihem" (in Pasuk 37).
In order to firmly hold together the west wall with the north and south walls.
See Pasuk 30.
Thereby holding the western wall firm against the northern and southern walls (Seforno).
