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How to make a hamster playpen
Build the walls of the playpen with something slippery.
A playpen needs to be a safe place for your hamster to explore, so it shouldn't be made of materials a hamster can climb or chew. Corrugated plastic is a great option as it is not only slippery, it can easily be cut to any size you need.
Another great option is a large rubbermaid-type container with tall sides. You can attach pieces of plastic together with anything from binder clips to duct tape.