WEIRD question

This is one of those questions that you kinda wanna know but never really wanna ask or know who, because Google certainly wont help you.

Now, Im assembling some project thingy, an IR receiver for your computer, and it fits right inside one of those small D-sub boxes (looks really good, Ill sell them later :)) but anyways, I noticed that the D-sub box comes with ALOT of screws and little pieces.

Thing is, there are:

2 large screws
3 hex thingies for the other side of the screw…nuts I think, not sure.
2 small screws
2 long screws flat on one end (these are the screws that u screw into your serial port – ignore if you dont know what i mean)
2 weird metal shaped pieces like /-\ that go on the end of those last screwns

and then, theres these 2 rounded things like a bracket you would use to hold a gas line to your house or osmething like that. What the hell are those for!