Exodus 26:28

“And the middle bar in the midst of the boards shall reach from end to end.] From east to west, as Jarchi interprets it; but this can only be said of the middle bar on the north and south sides of the tabernacle, for the middle bar at the west end was north to south: about this bar there is some difficulty, as that it is said to be “from end to end”, as if that only was; whereas it is reasonable to suppose that the rest were so likewise; it may be, they might come somewhat short of reaching the end, whereas this did entirely; or rather the truer reason is, because the rest of the bars consisted of various parts; whereas this was a long bar of one entire piece, reaching from one end of the…”

“(Compare Exodus 36:8-33.) The tabernacle was to comprise three main parts, the tabernacle Exodus 26:1-6, more strictly so-called, its tent Exodus 26:7-13, and its covering Exodus 26:14 (Compare Exodus 35:11; Exodus 39:33-34; Exodus 40:19, Exodus 40:34; Numbers 3:25, etc.). These parts are very clearly distinguished in the Hebrew, but they are confounded in many places of the English Version (see Exodus 26:7, Exodus 26:9, etc.). The tabernacle itself was to consist of curtains of fine linen woven with colored figures of cherubim, and a structure of boards which was to contain the holy place and the most holy place; the tent was to be a true tent of goats’ hair cloth to contain and shelter the…”

“reach: lit, flee, Ch1 12:15; Neh 13:28; Job 41:28; Pro 19:26 Exodus 26:29”

“"And the middle bar in the midst of the boards (i.e., at an equal distance from both top and bottom) shall be fastening (מבריח) from one end to the other." As it thus expressly stated with reference to the middle bar, that it was to fasten, i.e., to reach along the walls from one end to the other, we necessarily conclude, with Rashi and others, that the other four bars on every side were not to reach the whole length of the walls, and may therefore suppose that they were only half as long as the middle one, so that there were only three rows of bars on each wall, the upper and lower being composed of two bars each. Exodus 26:30”