Since these were more “simpler” challengers, I thought that it would be better again to show how I did them in just one topic.
Snapping:
As I’m using Blender 2.92, I had selected the “Auto Merge Vertices” button, so some of the vertices of the guardrail were merged to some vertices of the pyramid, so now I’m not able to change some areas of thae guardrail at the top. So, watch out for that if you have one of the most recent versions of Blender.
Array modifier:
Joining meshes:
Looks to be going well.
The merge verts automatically needs to be ‘on’ only very deliberately, when you want it to be, otherwise it is best in the 'off 'state.
Thank you. 
And you’re right.
Unfortunately, I only became aware of that after saving the file and when, in the following day, I decided that I didn’t liked the top half of the guardrail and I wanted to change it. But, because I left “Auto Merge Vertices” on all the time, when I wanted to modify some parts of the guardrail, that was no longer possibly, because the vertices of guardrail were merged with the vertices of the pyramid.
Oh well. Sometimes, it’s best to learn from your own mistakes.
