I viewed an episode of This Old House approximately a month ago, and saw a power hand tool that removed head and horizontal mortar joints in a brick wall without damaging the brick. The masonry sub was removing a portion of some decaying mortar while keeping the rest of the brick. They sawtoothed the end of the damaged brick / mortar joints and infilled with the undamaged brick and installed new mortar.
The hand tool, to my recollection, had two blades, one moving up while the other moved downward.
What is the generic name of the tool, and who manufactures such a device?