What is the term for creating a slight depression in laid mortar?

The term for creating a slight depression in laid mortar is referred to as a "furrow." This technique is often used in masonry to enhance the bonding between mortar and masonry units, such as bricks or stones. The furrow allows for better adhesion because it increases the surface area and creates a more complex joint profile, which can help prevent water infiltration and improve the overall durability of the masonry work.

Furrows are typically made using a trowel or similar tool and provide a functional aspect to mortar joints, which might be especially important in various construction and masonry applications. The practice is essential for both structural integrity and aesthetic aspects of masonry work.