How to keep room dark during flower?

I used 3-4 layers of the cut to size filter. Put it in the 6inch bottom vent hole and taped it to the bottom rectangular screen on the other side. Intake seems sufficient as the temps are steady as before. Cant really go in the tent to see if lights coming in, but cant see any light leaking out when the rooms dark. Thanks for the answers!

Hello. I have built for my tent a air damper. You take a cardboard box and inside you make several twist and turns to let air in and keep the light out. I painted the interior of the box flat black. took some extra cardboard, with black tape, stuck straight pieces cardboard inside like a maze. A intake hole and a outtake hole.. Hold it up to a light when done and no light shouldn't be seen looking in the holes. Sticky Velcro on the outside of the box if attaching to the screened air holes on the tent. Hope that gives you an idea. Chuck.

also getting black out tubing helps!