Strip the floor of any covering such as linoleum or carpeting.
Prepare the area to be repaired by sanding over and around it with the power sander. This helps the thinset concrete adhere to the floor.
Mix the thinset in the bucket according to the directions on the packaging.
Apply the thinset to the damaged area of the floor. Smooth it out with the trowel, working it so that it meets and slightly tapers over the edge of the original flooring.
Allow the concrete to set up briefly. While it is still wet retrowel the surface to ensure it is level and even with the original floor.
Recover the floor with carpet or vinyl.