In architecture, the capstone is the rock or stone placed on top of a wall. Unlike the cornerstone, which is the base of the structure and an important stone of the foundation, the capstone is the final stone placed on top that helps hold the structure together. The capstone, like the cornerstone, is an important metaphor for Jesus and His prominence as Head of the church and the kingdom of God.

In the Old Testament, Psalm 118:22 and Zechariah 4:7 mention a capstone. Zechariah correlates the word with the completion of the temple as Zerubbabel sets the capstone (Zechariah 4:7). The Lord tells Zechariah, “The hands of Zerubbabel have laid the foundation of this house; his hands shall also complete it” (Zechariah 4:9, ESV). In Psalm 118:22, the word could be translated as either “cornerstone” or “capstone.” This is the verse that Jesus quotes in His parable of the vineyard.