Concise Bible Dictionary:

As a protection for the body, see ARMOUR.

“253. Spear Large Shield.” From Manners and Customs of the Bible:

1. The chanith, “spear,” was a heavier weapon than the kidon. See preceding note. The word is rendered both “spear,” and “javelin.” It was the chanith with which Saul endeavored to strike David (1 Sam. 18:10-11; 19:9-1010And it came to pass on the morrow, that the evil spirit from God came upon Saul, and he prophesied in the midst of the house: and David played with his hand, as at other times: and there was a javelin in Saul's hand. 11And Saul cast the javelin; for he said, I will smite David even to the wall with it. And David avoided out of his presence twice. (1 Samuel 18:10‑11)
9And the evil spirit from the Lord was upon Saul, as he sat in his house with his javelin in his hand: and David played with his hand. 10And Saul sought to smite David even to the wall with the javelin; but he slipped away out of Saul's presence, and he smote the javelin into the wall: and David fled, and escaped that night. (1 Samuel 19:9‑10)
) and which at another time he aimed at Jonathan (1 Sam. 20:3333And Saul cast a javelin at him to smite him: whereby Jonathan knew that it was determined of his father to slay David. (1 Samuel 20:33)). This heavy spear had at its lower extremity a point by which it could be stuck into the ground. It was in this way that the position of Saul was naked while he lay sleeping in the camp at Hachilah, his spear being his standard (1 Sam. 26:77So David and Abishai came to the people by night: and, behold, Saul lay sleeping within the trench, and his spear stuck in the ground at his bolster: but Abner and the people lay round about him. (1 Samuel 26:7)). This lower point of the spear was almost as formidable as the head. The Arab riders of today sometimes use it to strike backward at pursuers, and it was with this “hinder end of the spear” that Abner killed Asahel (2 Sam. 2:2323Howbeit he refused to turn aside: wherefore Abner with the hinder end of the spear smote him under the fifth rib, that the spear came out behind him; and he fell down there, and died in the same place: and it came to pass, that as many as came to the place where Asahel fell down and died stood still. (2 Samuel 2:23)). The size of Goliath’s chanith, is expressed by the description of the staff and of the head; the latter being of iron, in contrast to the brass head of his kidon, and to his brazen helmet, cuirass, and greaves. See also note on Jeremiah 46:44Harness the horses; and get up, ye horsemen, and stand forth with your helmets; furbish the spears, and put on the brigandines. (Jeremiah 46:4) (#555).
2. The tsinnah, “shield,” was the largest kind of shield, and was designed to protect the whole body. This shield, as represented on the Egyptian monuments, was about five feet high, with a pointed arch above and square below. The great shield of the Assyrians, as is shown by their sculptures, was taller, and of an oblong shape, and sometimes had at the top an inward curve. The large shields were generally made of wicker work or of light wood covered with hides. They were grasped by a handle of wood or of leather. Goliath had man to bear his great shield before him. In the Assyrian sculptures there are representations of warriors fighting in this manner, with men before them holding the large shields, with the bottom resting on the ground, thus forming movable breastworks. The great shields of the Philistines seem to have been of circular shape.
The beauty of the figure used in Psalm 5:1212For thou, Lord, wilt bless the righteous; with favor wilt thou compass him as with a shield. (Psalm 5:12) is heightened by the fact that the tsinnah is the shield there spoken of. The Lord uses the great buckler for the protection of his people.

“498. Shields Oiled” From Manners and Customs of the Bible:

Shields were made of bull-hide, of two or more thicknesses, stretched over a frame of wood, and sometimes strengthened with metallic rims, and ornamented in various places by pieces of metal. An occasional rubbing with oil was necessary to prevent the leather from becoming dry and cracked, and to keep the metallic portions from rust. This was especially necessary on getting ready for battle, and hence to “anoint the shield” was equivalent to a preparation for war.