Pillars - Christian support
The material and function of structural pillars made them fittingly symbols of sturdy support. They would illustrate that which securely upholds. The Christian congregation could be called a "pillar and support of the truth" for through it Christians learn and gain understanding about the truth of God's Word.
1 Timothy 3:15 But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth.