What Are "Fillets" As Mentioned In KJV Exodus 27:10-11?

KJV Exodus 27:9-11,

9 ¶ And thou shalt make the court of the tabernacle: for the south side southward there shall be hangings for the court of fine twined linen of an hundred cubits long for one side:

10 And the twenty pillars thereof and their twenty sockets shall be of brass; the hooks of the pillars and their fillets shall be of silver.

11 And likewise  for the north side in length there shall be hangings of an hundred cubits long, and his twenty pillars and their twenty sockets of brass; the hooks of the pillars and their fillets of silver.

What Are "Tenons" As Mentioned In KJV Exodus 26:17?

KJV Exodus 26:17, Two tenons shall there be in one board, set in order one against another: thus shalt thou make for all the boards of the tabernacle.

What Are "Taches" As Mentioned In KJV Exodus 26:11?

KJV Exodus 26:11, And thou shalt make fifty taches of brass, and put the taches into the loops, and couple the tent together, that it may be one.

"Cherubims..."

KJV Exodus 25:18-20,

18 And thou shalt make two cherubims of gold, of beaten work shalt thou make them, in the two ends of the mercy seat.

19 And make one cherub on the one end, and the other cherub on the other end: even of the mercy seat shall ye make the faces of the cherubims be.

20  And the cherubims shall stretch forth their wings on high, covering the mercy seat with their wings, and their faces shall look one to another: toward the mercy seat shall the faces of the cherubims be.

What is a "cherub"?

Is a "cherub" a "singular" noun of the plural "cherubims"?