Strong's number H4043 magen :a shield (that is, the small one or buckler); figuratively a protector or defence.
#1 it was used as a deflector: The buckler's lightness and curved center made it excellent for deflecting attacking blades.
As for God, his way is perfect: the word of the LORD is tried: he is a buckler to all those that trust in him. Psalm 18:30
The LORD is my rock, and my fortress, and my deliverer; my God, my strength, in whom I will trust; my buckler, and the horn of my salvation, and my high tower. Psalm 18:2
My defence (buckler) is of God, which saveth the upright in heart. Psalm 7:10
. . . He is a shield (buckler) unto all them that flee for refuge in Him. Proverbs 30:5