the joining: the seam or facing edge where two pieces of cloth are fastened into one
This word belongs to the workshop. It comes from the everyday verb for joining things together (חָבַר), and it names what that work leaves behind: the place where two pieces meet. It is never used of joining people or ideas. Every time it appears, someone is telling a craftsman exactly where on a finished object the two halves come together, so that he knows where the loops, the clasps, or the rings belong.
All eight uses come from the building of Israel's portable sanctuary and the making of the priest's clothing. Six of them concern the tabernacle's linen panels. The ten panels were sewn into two groups of five, and the two groups were then fastened to each other. The word marks the facing edge of each group, where fifty loops on one side lined up with fifty on the other. The remaining two concern the ephod, the priest's shoulder garment, where two gold rings were fixed at the front just above the line where the shoulder pieces meet the woven band.
English versions part company over the curtain verses. Some keep the idea of joining and put the loops "in the coupling"; others name the group of panels that the joining creates and put them at the edge of "the first set" or "the second set". Both describe the same edge of the same cloth. The only difference is whether the word is heard as pointing to the seam itself or to the unit the seam holds together. A close relative from the same root (חֹבֶרֶת) fills the same slot twice, in Exodus 26:4 and Exodus 36:17, which suggests the two words were felt to be near enough to trade places.