In 'Call of Duty: Zombies', what's typically used to barricade doors and windows against zombies?

Wooden planks

Who is Shrek’s sidekick in the "Shrek" movies? In the film "Mean Girls", what day is famously celebrated? Who is the lead vocalist of the rock band U2? In what state did the Battle of Antietam take place? In Greek mythology, who was the god of the sea?