I made the second square opening for the second aluminum roof vent. But I also decided I installed the first roof vent too soon yesterday, because I installed the roof vent and put the roofing paper on top, which may make the roof vulnerable to leaks. I decided a better way would be to install the aluminum vents on top of the roofing paper and install shingles around the vents. So today I cut the second square opening, removed the aluminum vent I installed yesterday, installed wire mesh, and continued installing shingles. I will install the aluminum vents tomorrow when I install shingles up close to the vent openings.