Grow boxes help you create nearly any type of indoor garden. They must have vents in place to allow air flow around plants. Air circulation allows for even temperatures and diminishes plant stress. Once you cut in the vents, the fan used for venting pulls the air through the box and pushes it back out again to maintain a constant fresh air supply.
Stretch a measuring tape across the side of the grow box closest to the lighting. Find the center of the side and mark the position with a pencil. Place the fan above the marking near the top of the side. Trace a circle around the fan on the side. Remove the fan and cut the hole with a jigsaw. The size of the hole will be relative to the size of the fan; don't get a larger fan than needed for the project.
Place the fan into the hole so that it vents out. Install the fan into the hole according to the manufacturer's directions. Apply duct tape around the fan against the box to seal any air leaks left open by the cutout.
Measure across the width of the side opposite to the fan. Mark positions every 4 inches on the box. Drill a 1/2-inch hole at each position. This becomes the vent that draws the air through the box and vents the hot air out.
Attach and set up the timer for the fan and lights. This allows automation for the lights and fan to operate in conjunction with each other. Wire everything together according to the timer directions.