Over time the mortar joints between masonry units may have eroded away because cracked or missing mortar joints has allowed water to enter the interior of the wall and erode away the lime mortar. This process compounded by freeze/thaw cycles can cause the cracks to become larger and in some cases, walls to bulge as they continue to collect water and sediment, freeze, expand, and thaw. For this reason it is important to make sure the walls are solid between and behind the stone. Any voids in the masonry needs to be injected using historically appropriate materials and the wall stabilized before any repointing of the visual joints takes place. The final step in joint repair would be to match the color and strike of the original work.