Jacob saw the plan of ascension, one kingdom to another, as a ladder. Moses experienced it in the form of a mountain. Some ancients thought of the plan of salvation as three worlds or kingdoms stacked one above the other. Spanning these three worlds was a rope descending from the highest kingdom bringing connection to the lower worlds. Each of the three worlds is tied to the rope by a knot, and the knot is fastened with a nail (Vav). The temple is a knot symbolizing the connecting place between the worlds. Each level of temple worship has an altar which represents the Vav or nail in that world.
“The temple is thus thought of as the ‘bond of heaven and earth,’ as the ‘navel of the earth,’ and as the ‘pillar of the earth,’ that is, the central axis around which the world revolves. The temple represents ‘the Pole of the heavens, around which all heavenly motions revolve, the knot that ties earth and heaven together, the seat of universal dominion.’” [1 or LINK]
The rope is the center line of the temple, or the path to Lehi’s tree, or the straight and narrow path. The knot alludes to covenants. When people are married, the have tied the knot, they have made promises that bind them. In the case of the temple the knot or covenant is made binding by the nail or Vav, which represents the atonement.
“We stand in the middle position. This earth is the Old English middan-(g)eard, the middle-earth. The markas & scheckecirc; u er .s ti of the Babylonians means the knot that ties heaven to earth, the knot that ties all horizontal distances together (cf. fig. 37H, p. 151), and all up and down, the meeting point of the heavens and the earth. It is the middle point at which the worlds above and the worlds below join. This scale model of the universe is the temple. Of course, the word for temple in Latin, templum, means the same thing as template” [2 or LINK]
Sometimes this connection between the higher and lower worlds is a rope, trunk of a tree, vine, ladder, river, or even a spinal column. It is always the same template, showing the way back to God.
 Prof. Hugh Nibley, What Is a Temple? Chapter 8.
 Temple and Cosmos: Beyond This Ignorant Present, Hugh Nibley, Don E. Norton, Deseret Book, The Meaning of the Temple.
Also see: Water, Air, & Fire