fiberglass parts interior

Ive been searching around and cant seem to find info on how certain parts are secured to the rest of the car. . Please excuse me if Im not using the correct terminology as im a new to this and Im trying to get the whole picture before i give it a go. Lets take the interior stereo surround (bezel) as an example. I understand the process of molding and making the part except for how the clips on the back of the bezel are made. Some clips snap into place by being sort of half speared shaped and other look like a full spear, sometime with a metal clip attached to it, so the part is just pushed into place and u hear a click and it stays there. If Im looking at making a bezel from scratch and not modifying the orignal one how do I secure it ? even some door trims are held on with clips but the clips are held in place by the actual mold of the door trim.

Lets look at the front fenders of a car. Theres usually bolt holes along the top of the fender and just under the edge of the bonnet and a couple on the bottom aswell but if Im looking to make a replica of a factory fender they usually have a bracket or two that are located in the door jam. Are these brackets just made out of fiberglass seperately then attached? do people just make a custom metal bracket ? or is there a trick to doing it in one piece?

Hopefully I explained myself clearly and if anyone can point me in the direction of any video clips that explain this that would be great. Thank you

If you are going to go the custom route and break away from factory mounts and brackets, it will be up to you as to how technical or creative you wish to be in securing your newly created fabrication. You can inspect the factory brackets and then buy something similar from your local/internet hardware store. Hope that helps. And as always, reference pictures would help out to understand your situation/question.I have not failed. I've just found 10,000 ways that won't work.

When you do not know what you are doing and what you are doing is the best -- that is inspiration.