'A nail,' as in Zechariah 10:4, signifies supporting truth.

(Odkazy: Apocalypse Explained 355)

10747. Since love is the fire of life and what the life in anyone is like is determined by his love, it may be seen from this what heavenly fire is and what hellish fire is. Heavenly fire consists in love to the Lord and love towards the neighbour, while hellish fire consists in self-love and love of the world and in the consequent craving which goes with all the evils that pour out of these kinds of love as their source.