People in the Sixth Borough, like Computer-Head and Rubbish the Rat like to walk right into the truck and help themselves, so when it's hot, and Twan keeps the door open, he built himself this spider-web fence to keep out the riff-raff.
Twan also painted the van himself. He's a real asset to the neighborhood. Not only does he make his own sauerkraut but he drives out of state to buy tons of cigarettes so he can sell packs for 5 bucks each. The cops leave him alone because he gives them free breakfast sandwiches.