Uneven wood floors
Most drum sanders are designed to sand from left to right. You should get a DIY video from you rental supplier. The goal is to sand the floor flat, moving from the left side to the right. Feather up to the wall and feather the middle of the floor. Step sand by starting with 40g, 60, then final with 100. 60 and 120 on the edge sander. 120 with the buffer.