heres what i used to do.


cut a piece of cardboard to the exact size of your opening. cut a 'door' in the cardbord any size you wish.(cut 3 sides for a makeshift hinge) you now have a 4th wall for your cabnit with a door in it. set the cardboard back about one inch when you install it as the 4th (or FRONT) wall in your cabinet opening.

you now have a recessed wall in the front of your cabinet with a door for access. Use a black garbage bag and hang it like a blind over your door. Make it a bit smaller than yer cabinet opening but bigger than the cardboard door. now make exterior doors for your cabinet. (or most cabinets already have wood doors on them)

so you have a recessed cardboard wall with a door, BEHIND your real cabinet doors. if you drape a garbage bag over the cardboard door NO light will get out


you can seal the card board to the wall of the cabinet with aluminum foil tape.
SUPER CHEAP, SUPER FAST, SUPER EFECTIVE