and two frames for the two back corners of the tabernacle,
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 they shall be eight boards,.... Six at the west end and one at each corner, northwest and southwest: and their sockets of silver, sixteen sockets the same as those for the boards on both sides north and south: they were of the same metal, silver; and they were two under one board, to receive its two tenons as follows: two sockets under one board...
Exo 26:22-24 Six boards were to be made for the back of the dwelling westwards (ימּה), and two boards “for the corners or angels of the dwelling at the two outermost (hinder) sides.” למקצּעת (for cornered), from מקצּע, equivalent to מקצוע an angle (Exo 26:24; Eze 46:21-22), from קצע to cut off, lit., a section, something cut off, hence an angle, or corner-piece.
Commenting on Exodus 26:22-24