Mishnah here is going to talk about the Shulchan (table) and its structure. Mishnah says: There were four supports standing from the floor all the way up to the top and well past the Shulchan, serving to help bridge and connect its two sides. There were notches in the upper section of the supports where the poles would be inserted. The poles would support the bread, which would lie there in stacks of six. The poles would keep the stacks compact and make sure that nothing broke. The supports would support the loaves and keep them from breaking, as we just said.
Mishnah says: There were four supports standing from the floor all the way up to the top and well past the Shulchan, serving to help bridge and connect its two sides. The supports stood along the length of the Shulchan: two on one side and two on the other, to support each set of lechem hapanim (showbread), the two stacks. There were 28 golden rods between the loaves. Each rod was shaped like half of a hollow reed. To make sure that air flowed between the loaves and prevent them from becoming moldy, each rod rested on something like a semicircle. The rods were placed into the notches on each side of the Shulchan, so the bread would rest there with airflow between the loaves. There were 14 rods for one side of the bread and 14 for the other side. The Torah tells us that the old bread was removed from the Shulchan every week, and it was miraculously kept hot and served to the Kohanim (priests), while new bread was placed there.
Here we’re going to talk about the law concerning the rods. Neither arranging the rods for the new stacks of bread nor removing them from the old stacks overrides the laws of Shabbat. The rods were not allowed to be removed or replaced on Shabbat. There is an issur de-Rabbanan (rabbinic prohibition) of binyan u'setirah, building or demolishing, and the rods fell under this idea. Even though they were essential and needed to prevent mold, they could wait a day. No mold was going to grow within that one day. Therefore, this did not override the laws of Shabbat, and it was forbidden to remove or replace the rods on Shabbat.
Ela nichnas me'erev Shabbat veshomtan. The Kohen would enter the Hechal (sanctuary) on Friday and remove the rods from between the loaves. He would place them on the floor along the length of the Shulchan. That’s what he would do with them. There was no room for the rods on the Shulchan itself, so he placed them on the floor. Every Shabbat, the old stacks of bread were removed from the Shulchan and the new stacks of bread were arranged in two stacks, but there were no rods there. After Shabbat was finished, the Kohen would return and insert rods between the loaves.
Now we’ll explain why the Kohen would lay the rods on the floor. He would lay them down lengthwise, not widthwise. Kol hakelim shehayu baMikdash, arkan le'orko shel bayit. All the kelim, the vessels of the Bet HaMikdash (sanctuary), like the Shulchan and the Menorah (lampstand), were placed lengthwise, along the length of the sanctuary, in the east-west direction. For this reason, the Kohen did the same thing: He rested the rods in the east-west direction as well. So, when he removed the rods on Friday in order to take the bread on Shabbat, he placed them on the floor in this direction, like the rest of the kelim of the Bet HaMikdash.