Chimney repointing (often called tuckpointing) is the highly skilled process of grinding out cracked, decayed, or missing mortar from between a chimney's bricks and packing the voids with fresh, weather-resistant mortar. Because chimneys stand completely exposed to the elements, their mortar joints absorb the brunt of wind, rain, and freeze-thaw cycles. Repointing restores the structural integrity of the chimney stack, prevents water from penetrating the masonry, and stops total structural failure before costly rebuilding becomes necessary.