Exodus 36:21 in the World English Bible
Ten cubits was the length of a board, and a cubit and a half the width of each board.
Context
20 And he made boards for the tabernacle of shittim wood, standing up.
21 The length of a board was ten cubits, and the breadth of a board one cubit and a half.
22 One board had two tenons, equally distant one from another: thus did he make for all the boards of the tabernacle.