I decided to try making some of these because of their price in stores and how much cardboard I simply throw away in a month. I gathered all of the cardboard boxes I could find and cut them into 2″ wide strips on an old paper guillotine. This was more labor intensive that I expected. I glued the strips together with Elmer’s wood glue and clamped them for 24 hours. I made two separate units, which seem equal in durability to the store-bought models. The cats show no preference.