central pillar; main pillar
Literal architectural term for the main supporting pillar of a building. Compare 大黒柱, which often carries a stronger traditional or symbolic nuance.
See also: 大黒柱
The central pillar of this temple is made from a thousand-year-old cypress.
principal post; backbone; key figure
Figurative use for a person or thing that serves as the central support of an organization, community, or project. Similar to 大黒柱 in figurative contexts, but 主柱 can sound slightly more formal or structural.
See also: 大黒柱
He is relied upon as the backbone of local volunteer activities.