The middle bar, or “center crossbar” (Contemporary English Version), refers to the third of five crossbars at each of the three sides. Halfway up the frames is literally “in the midst of the frames.” Shall pass through from end to end is literally “sliding from the end unto the end.” It was evidently one long bar that extended the full length of each side. That means that the north and south sides each had a middle bar thirty cubits long, and the west end had a middle bar ten cubits long. The length of the other four crossbars for each side is not indicated.

Shall pass through means that this middle bar is to be inserted through the gold rings mentioned in the next verse. It may be necessary in some languages to advance this information from verse 29 and say “shall pass through the rings of the frames from one end to the other.” Good News Translation avoids this by saying that the “crossbar … is to extend from one end of the Tent to the other.” Contemporary English Version has “with the center crossbar running the full length of the wall.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .