Exodus 36:11-13

Then they made loops of blue material along the edge of the end curtain in one set, and the same was done with the end curtain in the other set. They also made fifty loops on one curtain and fifty loops on the end curtain of the other set, with the loops opposite each other. Then they made fifty gold clasps and used them to fasten the two sets of curtains together so that the tabernacle was a unit.