Exodus 26:4-6

And you shall make loops of blue yarn on the edge of the curtain on the selvedge of one set, and likewise you shall do on the outer edge of the other curtain of the second set. Fifty loops you shall make in the one curtain, and fifty loops you shall make on the edge of the curtain that is on the end of the second set, that the loops may be clasped to one another. And you shall make fifty clasps of gold, and couple the curtains together with the clasps, so that it may be one tabernacle.