What type of jointer is referred to as a sled runner?

The term "sled runner" specifically refers to a concave jointer used for horizontal joints. This tool is designed to create a smooth, concave profile in the mortar between bricks or masonry units, which helps facilitate water drainage and can enhance the visual appearance of the joint. The concave shape effectively compresses the mortar, making it less likely to crack and improving the long-term durability of the joint.

Using a concave jointer for horizontal joints is particularly effective because it provides a tight seal that can help prevent moisture infiltration, which is crucial in maintaining the integrity of masonry structures. The technique of using this type of jointer is a standard practice in masonry to achieve a professional finish.

In contrast, while a concave jointer for vertical joints can also be beneficial, it does not specifically relate to the term "sled runner," which is more often associated with horizontal applications. The flat jointer and pointed trowel mentioned in other options serve different purposes in masonry work and do not match the specific function described by the term "sled runner."