Two tenons shall be in each board for binding one to another. Thus you shall make for all the boards of the tabernacle.
Exodus 26:17
Surrounding context
26:16 Ten cubits shall be the length of a board, and a cubit and a half shall be the width of each board.
26:17 Two tenons shall be in each board for binding one to another. Thus you shall make for all the boards of the tabernacle.
26:18 And you shall make the boards for the tabernacle, twenty boards for the south side.