Black Plague - stuck after cameras in Chemical Lab

[Brob]

Just got past the sweeping camera/wall switch areas, and made it into the chemical lab.

For some reason though, I can't tip over the shelf to block the door! I've tried every physical way possible. Resorted to reading walkthroughs that casually mention using the shelf to block the door.

The mouse cursor changes to a hand (usually) but then I can't move the shelf over?

What'd I miss?

[Desperate4God]

It's been a while since I played Black Plague, but I remember having to "pull" the shelf in bursts. Another way to explain it: you're having to tug at it because it's so heavy. I don't think you can simply pull it like you normally would,

Spoiler below!

because it's weight keeps the Infected permantly out of the room.