You shall make the frames for the tabernacle: twenty frames for the south side;
Very particular directions are here given about the boards of the tabernacle, which were to bear up the curtains, as the stakes of a tent which had need to be strong, Isa 54:2. These boards had tenons which fell into the mortises that were made for them in silver bases. God took care to have every thing strong, as well as fine, in his tabernacle.
Commenting on Exodus 26:15-30
And thou shall make forty sockets of silver under the twenty boards,.... Or bases (s), and which were properly the foundation of the tabernacle, on which it was settled and established; these sockets were the mortises for the two tenons of each board or plank to be placed in, and were as broad as the plank, and, joining each other, made one entire basis for...
Exo 26:18-21 Twenty of these boards were to be prepared for the side of the dwelling that was turned towards the south, and forty sockets (אדנים foundations, Job 38:6) or bases for the pegs, i.e., to put the pegs of the boards into, that the boards might stand upright; and the same number of boards and sockets for the north side.
Commenting on Exodus 26:18-21