I mirror Matt's sentiments in that I won't be discussing any specific symbols or rituals that are administered in the temple; they are quite sacred to me, and excessive public discussion on their nature cheapens them in my opinion. I don't mean to offend you if this is an honest inquiry, it's just how I feel on the matter.
However, I can speak somewhat on the origin of the symbols themselves, or rather the unimportance of the same.
I've transcribed an excerpt from an excellent interview of LDS scholar Terryl Givens by the podcast Mormon Stories. (Part four, beginning at around 59:30)
TG: All great religion is plagiarism, especially in the Mormon conception of things because it's not possible to create anything new, right? It was all known to Adam. There's this gospel that we're all trying to reach back and grope toward and reconstitute in its entirety and fullness. So if that's the paradigm you begin with then there's no such thing as novelty and innovation in religious thought, we're just trying to recuperate.
There are other people, like I think Michael Smith is one, who are doing really interesting work on the influence of Masonry in early Mormonism. I certainly don't know the full story, but, you know I'm reminded of a priest that I used to work with who came back from a mass he had just celebrated where he used beer for the wine and potato chips for the wafer. And I remember at the time I thought, that was a little bit over the top and blasphemous... and, you know, to some extent maybe it was, but the point he was trying to make to his congregation was, it doesn't matter what symbols we use. It doesn't matter. And we could rewrite the temple ritual tomorrow and use Boy Scout signs and handshakes and it wouldn't matter. It's so immaterial what are the actual, right, physical aspects of the ritual that we go through in the temple.
Joseph found Masonic ritual adaptable in ways that suited his purposes. He seemed to think that the Masonic ritual was an actual if corrupted inheritance from an ancient endowment. Now, the best scholarship today believes that Masonry is a fairly late invention out of whole cloth in the 17th century, right? I don't know where Masonry comes from, I don't know what its relationship is to an original Adamic endowment, and I don't care. Because I don't go to the temple because I believe that the actual ritual I am engaged in has any inherent value. What has value are the covenants that we make, the promises that we receive and the relationships that are eternalized. And so I just say, well bravo to Joseph Smith for finding a system that was quick and readily adaptable to his purposes.
MS: So, the Masonic stuff, you know the ritual, is sort of like the delivery vehicle for the doctrine and the covenants, is that what you're saying?
TG: Exactly.
(Emphasis mine)
This is in no way authoritative, as Terryl Givens is not in a general leadership role in the LDS Church. However, his opinion on the matter seems true to me. To summarize, the form that the symbols take are not necessarily crucial in their own right. They are a delivery mechanism for the sacred aspects of the Gospel that we partake in in the temple.
