Is it possible for me to use lids while the holes are made from using "Reference Plane" and "Cut Extrude"? I've been trying to select the holes but it doesn't work. Are there any alternatives in order to create holes at a certain angle of the pipe?
You can use hole wizard. Check if this helps: Drilling a Hole on Cylindrical Surface
You can use hole wizard. Check if this helps: Drilling a Hole on Cylindrical Surface