Explanation:
Random rubble masonry is a type of masonry in which stones are placed without any order or pattern. These stones are not of uniform size and shape. In random rubble masonry, the face stones are chisel dressed. Let's discuss what chisel dressing is and why it is used.

Chisel Dressing:
Chisel dressing is a process of shaping stones using a chisel and hammer. In this process, the surface of stones is made smooth by removing the protrusions with the help of a chisel. The chisel is a long, pointed tool that is used to cut or shape hard materials such as stone or metal. The hammer is used to strike the chisel and make it cut the stone. This process is used to create a flat surface on the stone.

Why chisel dressing is used:
Chisel dressing is used to create a smooth surface on the face of the stone. This is done to improve the appearance of the stone and make it more suitable for use in construction projects. When the stones are chisel dressed, they can be easily placed on top of each other to create a strong and stable structure. Chisel dressing also helps to reduce the amount of mortar required to hold the stones together.

Conclusion:
In random rubble masonry, face stones are chisel dressed to create a smooth surface and improve the appearance of the stone. Chisel dressing is a process of shaping stones using a chisel and hammer. This process is used to create a flat surface on the stone and reduce the amount of mortar required to hold the stones together.