The image of a rock is an aspirational symbol for who we want to become as men: foundational, steadfast against outside forces, dependable. With St. Peter being named by Christ as the rock, and being the namesake of our church, the symbolism of a rock has a direct tie to our church, the Church, and Christ. There are more layers which I’ve written out in The Meaning of the Name.
The shield
Keys Logo · Shield v2
Keys, hammer and sword
Shield v4
Shield v5 · Hammer
Shield v5 · Sword
The quartered shield
Shield v8 · Axe
Shield v10A · Tilted Sword
Shield v10B · Tilted Sword
Shield v10B · Rock
Where the symbols come from
The Sacred Heart
Catholic devotion to the Heart of Jesus expresses his love for us. St. Margaret Mary Alacoque helped spread this devotion in the seventeenth century.