In the two sides - Rather, at the back.

And two boards shalt thou make for the corners of the tabernacle in the two sides. For the northwest and southwest corners, in the north and south sides; concerning which Dr. Lightfoot thus writes (t): and the west end had six planks entire, besides a plank at either corner, joining end and sides together; these corner planks were of the same breadth that all the others were, and, thus set, the middle of the breadth of the one plank was laid close to the end of the south side, or to that plank that was furthest west; so that a quarter of a yard of the breadth of the corner plank was inward, to make up the tabernacle breadth, a quarter was taken up with the thickness of the side plank to which it joined, and a quarter lay outward: thus at the southwest, just so was it at the northwest corner: then count; the two corner planks were inward a quarter of a yard apiece, and the six planks that stood between them of three quarters apiece, behold five yards, just the breadth of the house between wall and wall: these corners knit end and side together, and were the strength of the building; as, adds he,"Christ is of his church, making Jews and Gentiles one spiritual temple.''
(t) Ut supra. (Works, vol 1. p. 719.)