Attaching new case fan

[stuarths]

I am replacing my stock fans on a Lian-li v1000. The rear fan attaches directly to the back of the case with four of these black pop-up expansion pins. Can someone tell me

1) what these pins are called
2) why mine won't stay down (the fan seems to have pin holes same diameter and depth)
3) where can I get the pins

I called a mod shop and these things are supposed to simply reattach with a little effort and the back of a screw driver handle.

Does anyone have any experience with this that they can share? Thanks.

 

[halw]

1& 3 see this link toward bottom.

 

[professor1942]

Separate them completely and put the wider part in all the way before putting the skinnier 'pin' in.