Exodus 36:23

The length of a board was ten cubits, and the breadth of a board one cubit and a half.

One board had two tenons, equally distant one from another: thus did he make for all the boards of the tabernacle.

And forty sockets of silver he made under the twenty boards; two sockets under one board for his two tenons, and two sockets under another board for his two tenons.

And for the other side of the tabernacle, which is toward the north corner, he made twenty boards,