Learning about body bolts

OK as I have said before I'm learning. Every day I learn something new!
When they assemble trucks are things such as body brackets pre-threaded? For
example I'm working trying to install the rear mud flaps. Part of the process is to remove the bolt located just behind the rear wheel well under the rolled edge of the body panel. This bolt holds the lower side panel to a support type rod/bracket to make things rigid. Mud flap instructions show there being a nut but not on my truck. The bracket is the nut on my 2006. On both sides the bolts were stripped before I even tried to disassemble. So I went and bought a tap while I was buying new bolts. I used the tap to chase the threads in the brackets. Instead of just chasing threads it felt like I was cutting original threads.
So the question I have is when this was assembled at the factory did the rod.bracket have threads before they assembled? Or is the body bolt supposed to be a self threading bolt? I see where the end of it is special to help with finding the hole during assembly. And since both were in such bad shape it isn't just coincidence. Now that I have actually taped new clean threads the new body bolt go in and out like they were made for each other.
I'm thinking for the factory to pre-thread the bracket cost money. So instead the assembly person has an air driven tool to speed up the effort. The bolt is placed in tool, end of bolt helps them find the hole, air tool has enough torque to cut threads as it installs the bolt, and provided you never take it apart to put mud flaps on it will stay together for ever. But if you try to remove the bolts sometimes it comes out fine and other times you get what I got which is a chance to gain experience and learn something new.
I do appreciate all input! Like I said I can't learn unless I ask questions and work on stuff.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

an on topic question? Is there something wrong with you?
beekeep
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The bolts are sometimes self tapping. They are designed to cut the thread as you screw it in.
Al
Al
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.