OK, this is a really dumb question. I'm sure the answer is somewhere in the forum if only I knew the name of this thing. Under the hood, there are black plastic fastreners that casually look like phillips head screws. If I pop up the center, they release. 1) What are these called? 2) What is the proper way to remove them? I am concerned that repeated removal using my carefull but unsatsifyingly clumbsy method will eventually break them. Clearley this is a fastener designed for assembly.