Which action is used when filling a joint to prevent leaks?

Caulking is a critical action used when filling a joint to prevent leaks, particularly in roofing and other construction applications. It involves applying a flexible material that can seal gaps and spaces where two surfaces meet, effectively preventing water, air, and other elements from penetrating through these joints.

Caulking materials are designed to expand and contract with temperature changes, accommodating movement without breaking the seal. This property is essential in maintaining the integrity of the roofing system, especially since roofs are subjected to varying weather conditions. By ensuring joints are properly caulked, the risk of leaks and subsequent damage to the structure can be significantly minimized.

In contrast, capillary action refers to the ability of a liquid to flow in narrow spaces without the assistance of external forces, which is not a method used for sealing joints. Chasing, while it may refer to creating a groove or recess for a joint, does not directly fill a joint. Cement, though it can be used in certain situations, is not the preferred material for sealing joints due to its rigidity and potential to crack, which could lead to leaks over time. Thus, caulking is the appropriate method for effectively sealing joints against leaks.