Forty sockets of silver. Nothing is said of the shape of these "sockets." They were certainly very massive, as each contained a silver talent (Exodus 38:27), and thus weighed from eighty to ninety pounds.
It has been supposed that they stood on the ground, and formed a sort of continuous base, out of which the planks rose. But this would have constituted a very unsafe structure. Kalisch is probably right in his view, that the sockets were let into the ground resembling those at the bottom of a gate, into which the bolt is pressed down.
Each socket received one of the "tenons."