The Mishkan had two abutting wall planks, which ran from east to west and from north to south, meeting at the corner of the Mishkan. They are described as to’amim milmatah, coupled together on the bottom. The words to’amim and teumim have the same root, which means twins. Thus, although being two distinct units, separated by the Adanim, silver sockets at the bottom (in which pegs of the planks were placed), they fitted and complemented one another. The tops of the planks had to be tamim, matched up – completely, united by the tabaas, ring, that passed over them.
Horav Shimon Schwab, zl (quoted in Rav Schwab on Chumash), observes that the construction of the Mishkan serves as (among other lessons) a metaphor for the building of the Jewish marriage and, by extension, the Jewish home. A man and a woman are two distinct individuals, with variant personalities, who share common interests. Based upon their individual talents and strengths, they will approach each specific endeavor differently. Twins are born together, often have similar appearances, but maintain different personalities and talents. Nonetheless, they have a unique relationship unlike the average two siblings. Concerning the physical, mundane aspects of marriage, the young couple are toamim milmatah, coupled together on the bottom. Coupled is sufficient, since, after all, they are different. On the other hand, concerning the “top,” hashkafos, Jewish philosophical outlook, spiritual values, etc., a husband and wife must do more than merely complement one another. They must be yachdav, completely united, unified as one, like the kerashim which yachdav yiheyu toamim.
This accord (fusing of the minds) is created via the tabaas, single ring, over both planks. The Rav says that this is the source for the custom of using a ring as the medium of marriage, as opposed to any other item of value (Tosfos Kiddushin 9A). (Perhaps this is why we should maintain the custom of a single ring ceremony. Two rings imply two hashkafos.) The Jewish home is referred to as a mikdash me’at, a mini sanctuary. The wedding accentuates the similarities between the sanctity of the Jewish marriage (a union of holiness, hence, Kiddushin) and the kedushas, sanctity, of the Mishkan.