They made the breastplate square by doubling it; a span was its length and a span its width when doubled.
Exodus 39:9
Surrounding context
39:8 And he made the breastplate, artistically woven like the workmanship of the ephod, of gold, blue, purple, and scarlet thread, and of fine woven linen.
39:9 They made the breastplate square by doubling it; a span was its length and a span its width when doubled.
39:10 And they set in it four rows of stones: a row with a sardius, a topaz, and an emerald was the first row;