I didn't make it!
The walkthrough says drop through the hole. In this room there will be two supply crates, but if you run on the platform they are on, it will drop, so use the Gravity Gun to get the crates, if you fall, don't worry, there is a ladder to get back up, but you can drop down and die. Head to the gate the houses all the Zombies and open the gate. That is the problem I blasted the boards off the gate there is nothing to prevent me going through the gate but it won't open. Everything has worked in all episodes but this one. Any suggestions.