French drags are somewhat the equivalent of the plane in carpentry. They are used for soft stones and consist of blades set at alternating angles, between 15 and 30 degrees, over the length of a block of wood. The blades are toothed to provide even removal of surface material. Some drags can be fitted with specially shaped blades to follow convex surfaces. it is important to always run a drag towards the center of a block and never out across an edge. These tools are especially useful for final preparation of large surfaces..