Tomorrow is not only the start of a new year, but also the start of my hedgehog ownership! To prepare, I had to finish the cage. Above are my tools: power-drill (thanks Simo!), exacto-knife, and space heater. The heater is for keeping my hedgehog warm, but also useful for keeping the plastic warm while making holes into it - I unfortunately managed to still get some cracks in the plastic. After tracing an outline of where the tunnel would be, I used the power-drill to make holes along the edge. With the exacto-knife, I cut between the holes, and cleaned up the edges.
After cutting out the hole, the tunnel is wedged in. I used a 4" PVC connector pipe bought from a hardware store. Ta-da, tunnel complete!