Exodus 26:17,19 Two tenons shall there be in one board, set in order one against another: thus shall you make for all the boards of the tabernacle. Torrey's Topical Textbook
Exodus 36:22-24 One board had two tenons, equally distant one from another: thus did he make for all the boards of the tabernacle. Torrey's Topical Textbook
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Concerning the Tabernacle which Moses Built in the Wilderness for ... ... And after this manner was the tabernacle reared. ... every way evenly fitted to it, and had no eminences ... rings belonging to each of the longer boards, and passing ... /.../josephus/the antiquities of the jews/chapter 6 concerning the tabernacle.htm