Though brick and stone can last a century, the mortar between them deteriorates more quickly. Loose mortar or cracked mortar joints can allow water to seep behind the brick to inflict severe damage and threaten the stability of the chimney. Tuckpointing, also known as repointing, is the process by which deteriorating mortar between the bricks is replaced. Essential to this process is the act of grinding out the old and weakened mortar with a diamond-blade concrete saw. New mortar is then applied, in a color that matches the old mortar, restoring the integrity of the chimney structure.