Tuck pointing becomes necessary when mortar develops cracks and holes. These can come from various causes, and the entrance of water into hairline cracks, which during the winter can freeze and expand, widening the holes. And finally starts to loosen stone from mortar bond
WHAT IS TUCK POINTING
Tuck pointing is done by removing old mortar to depth of sound mortar and replacing it with new mortar of a similar consistency.
Why Tuck Point
Stone last forever, far longer than mortar. To maintain a waterproof seal, occasional maintenance of the mortar becomes necessary over the life of the structure.