Exodus 26:17

שתי ידות לקרש האחד TWO TENONS THERE SHALL BE IN ONE BOARD — They cut out the lower part of the boards in the middle to a height of one cubit leaving one fourth of its width on the one side and one fourth of it on the other side. These pieces on each side of the boards were the ידות, the tenons. Thus the part cut out was one half of the breadth of the board (¾ cubit) in its centre. Now these tenons they fixed into the sockets which were made hollow. The sockets were one cubit in height and they lay in a line forty of them, one close against the other. The tenons of the boards that were fixed into the sockets were then cut away on three sides, the depth of the portions thus cut away being equal to the thickness of the rim of the sockets, so that when the boards were fixed in the sockets the wood of the board would cover the entire top of the socket. For if this were not so (if the tenons were not cut away on their outside edge) there would have been a space between one board and the next equal to the thickness of the rims of two sockets which would have separated them. That is what is meant when it says, (v. 24) “and they shall be coupled together beneath” — that they should cut away the sides of the tenons in order that the boards should join closely one to the other. משלבת means made like the rungs (שליבה) of a ladder and separated from each other and planed at their ends in order that they could be inserted into the hollow of the sockets like a rung which is fixed in the hole in the ladder’s uprights. אשה אל אחתה ONE TO THE OTHER — i. e. the tenons should correspond exactly one to the other; the meaning is that the portions cut away from the fronts and backs shall be precisely equal, one portion cut away having the same measurement as another portion cut away in order that of two tenons one should not diverge from a straight line towards the front and the other diverge towards the outside (the back) in reference to the thickness of the board which was one cubit. The Targum renders ידות by צירין, pivots, because they resembled, in one respect, the pivots of a door which are inserted in the hole in the threshold.

שְׁתֵּ֣י יָד֗וֹת לַקֶּ֙רֶשׁ֙ הָאֶחָ֔ד מְשֻׁ֨לָּבֹ֔ת אִשָּׁ֖ה אֶל־אֲחֹתָ֑הּ כֵּ֣ן תַּעֲשֶׂ֔ה לְכֹ֖ל קַרְשֵׁ֥י הַמִּשְׁכָּֽן׃

Two tenons shall there be in one board, connected one with the other: thus shalt thou make for all the boards of the tabernacle.