I know you can do this, but its not in the manual or command list that I could find.

How you select all units of a particular class at once?

For example, if I want to select all the siege frigates in a particular system, what is the clicking that I have to do?

I know this seems like a stupid question, and I've been playing without knowing this for days now, but I simply can't remember and a quick run through of the tutorials didn't help.

Thanks.