I used to refinish antique wood floors. I walked into a 100 year old bungalow with hardwood oak floors. I stood in the kitchen with my hands on my hips for 5 seconds looking at the floor and fell through! It hurt like hell and I only stopped when my arms were up to my shoulders. Hard to climb out too. I did floors for over 10 years and thats the only time that happened. I used a made in Germany Hummel floor sanding machine. The machine and I together weighed around 400 lbs.