How do I use the medic's shield on Mann vs Machine?

For a while now I have been playing Mann vs Machine on TF2. I see everybody using these large shields as Medic, which I can also see in the upgrade menu.

So I was wondering, how do I activate this shield with the default keys?

If it helps any I play on PC.


Solution 1:

The default control is Mouse3. This is your middle mouse button- clicking the mousewheel.

If you want to change the control, it is listed as Special Attack on the controls menu.