Bede

From this it appears to have been the case that the borders of two pieces were joined together from top to bottom on both sides into a doubled garment. In [this] way … half of the garment would be visible to the eyes of those looking at it from the outside while the other half would be concealed on the inside, but the joined borders of the two would come all the way down to the lowest point below. What else are we to understand by means of this type, except that while we are displaying good works on the outside before our neighbors, we must keep them unblemished on the inside before the Lord?