Exodus 26:20-24

and for the second side of the tabernacle, on the north side, twenty boards,

and their forty bases of silver; two bases under one board and two bases under another board.

For the back of the tabernacle, to the west, you shall make six boards.

You shall make two boards for the corners of the tabernacle at the back.

They shall be double beneath, and together they shall be complete to its top to the first ring; this is how it shall be with both of them: they shall form the two corners.