One of the big advantages of this design is that it is simple, efficient, and made with readily available materials. This is the view under the floor, where the 4 corners of the sack are hooked to nails. We can also the tip of the standard funnel which empties into a 3-liter beverage bottle, which connects to a 12-meter perforated hose. More info and TEXTO EN ESPAÑOL at Chris Canaday's blog, www.inodoroseco.blogspot.com