Exodus 26:19-21

And thou shalt make forty sockets of silver under the twenty boards; two sockets under one board for his two tenons, and two sockets under another board for his two tenons. {tenons: Heb. hands} And for the second side of the tabernacle on the north side {there shall be} twenty boards: And their forty sockets {of} silver; two sockets under one board, and two sockets under another board.