Steel trowel/steel blade that's especially good for spreading wall and floor compounds.

Steel trowels/smoothing blades are meant for spreading compounds evenly over a large area. They're available in several different sizes. With bigger blades, you can spread larger amounts of compound faster, but the bigger the blade, the heavier the spreading work gets.

Compounds are spread onto the surface by pulling or pushing the blade against it. This way, the uneven spots on the surface get filled evenly.