Cooling Rubber fan mounting pins

These seem to come in two different sizes. A short one and a long one. I'm guessing they're for different mounting "situations", but where should i use them?

I haven't seen them in action yet and there are several ways you can go about mounting the same kind of pin, so can someone explain them to me? With pictures if possible.

Thanks

 

Use long ones:


Use short ones:


Can you see the difference between the open/closed frame? (Look where the screws would go in!)

 

Ah, yes, now i see. It all makes sense now, thanks mate! (never had a closed frame fan before)

+rep

 

I hadn't either until I bought some of that model Yate Loon. In fact, the only way I could find a picture of one was to go to the website I bought the fans from, so as far as I know they're not too common. However, you'd be annoyed if you went to install it and the rubber mount didn't fit all the way through.