If you made a hole for a vent fan... then why dont you install a vent fan?
Why do you want to cover it?

you can probably cover it with the same materials that you built the cabnet with.... correct?

cheers
Garden Knowm Reviewed by Garden Knowm on . Garden Knowm Hey dude...its me again...just a few questions again... 1- is there such a thing as 2 much light? i now have 2 150watt CFLs..2 100 watt CFLs and 2 75 watt CFLs...in my new grow box..*patented by me...made by my barehands*...they are over my plants by about 1-2 inches...with 2 4" fans constantly blowing on them...with on nice fan blowing outward for my ventalation..which brings me to my next question... 2-what do i use to cover the hole in my box for the ventalation fan?...i figure that your Rating: 5