26 And thou shalt make bars of shittim wood; five for the boards of the one side of the tabernacle,
27 And five bars for the boards of the other side of the tabernacle, and five bars for the boards of the side of the tabernacle, for the two sides westward.
28 And the middle bar in the midst of the boards shall reach from end to end.
26 וְעָשִׂ֥יתָ בְרִיחִ֖ם עֲצֵ֣י שִׁטִּ֑ים חֲמִשָּׁ֕ה לְקַרְשֵׁ֥י צֶֽלַע־הַמִּשְׁכָּ֖ן הָאֶחָֽד׃
27 וַחֲמִשָּׁ֣ה בְרִיחִ֔ם לְקַרְשֵׁ֥י צֶֽלַע־הַמִּשְׁכָּ֖ן הַשֵּׁנִ֑ית וַחֲמִשָּׁ֣ה בְרִיחִ֗ם לְקַרְשֵׁי֙ צֶ֣לַע הַמִּשְׁכָּ֔ן לַיַּרְכָתַ֖יִם יָֽמָּה׃
28 וְהַבְּרִ֥יחַ הַתִּיכֹ֖ן בְּת֣וֹךְ הַקְּרָשִׁ֑ים מַבְרִ֕חַ מִן־הַקָּצֶ֖ה אֶל־הַקָּצֶֽה׃
There were five bars for each wall of the Tent of the Mishkan...
When positioned on the walls, it would look like this...
Here is a view on the bars at another angle...
The length of the bars would be, most likely, defined by... the size and location of the Altar Of Incense...
Here is a top view for you, to better reflect the idea...
Therefore, there were:
1) For North and South walls of the Tent, for each of the walls - two bars 19 cubits in length, two bars 10 cubits in length and one bar (the middle bar) - 30 cubits in length.
2) For West wall of the Tent - four bars 4 cubits in length and one bar(the middle bar) 9 cubits in length.
Location of the bars on the walls appear to be related to the length of the curtains, and it was:
1) For North and South walls of the Tent, for each of the walls - one 19 cubits bar and one 10 cubits bar were located 1 cubit off the ground. One 30 cubits bar (the middle bar) was located 5 cubits off the ground, and one 19 cubit bar and one 10 cubit bar were located 9 cubits off the ground.
2) For West Wall of the Tent - two 4 cubits bars were located 2 cubits off the ground, one 9 cubit bar (the middle bar was located 5 cubits off the ground, and two 4 cubits bars were located 8 cubits off the ground.
The thickness of the bars is not given, but it would be logical to assume that it would be equal to that of the bars that were used for the artefacts of the Mishkan... perhaps a hand-grip diameter or ~ 0.06-0.07 cubits(3-4cm)
I have to admit though, that I'm not 100% certain about the length of the bars. I'm still trying to figure out the logic behind their positioning and dimensions...
Here is also a little excerpt from the book called "The book of Exodus: with introduction and notes" By Alan Hugh McNeile.
In his book he documents an opinion of Prof. A. R S. Kennedy, whose insights on some details of the Tabernacle I find very appropriate and useful in my attempt in reconstruction of the Tabernacle...
The frames are strengthened by five bars running through rings. One unbroken bar ran continuously the whole length of a side of the structure, and the other four presumably ran above and below it, at the top and the bottom, two half-length bars in each case being placed end to end, and reaching the whole length. Thus, when inserted in position, there were three full-length bars; and this renders it probable that each frame had three cross-rungs, over which the bars ran. Further advantages of Kennedy's scheme will be seen later.
You can find this book in my Google Library, as well as other books on the Mishkan (see my link bar)