No screws or nails needed. The 4 measurement is of the depth of the shipper box with the unassembled room in it. The room will come unassembled and the panels are laid flat on top of each other in the box.
The 5 panels (5 walls of the entire room including ceiling) are laid on top of each other. Each wall panel's thickness is 5/16 inches (8mm). The finished assembled room actual measurements are 24 3/4 x 19 x 21 inches.
The wainscoting is not raised but carved into the wall panel. You can feel it with your finger. The entire room is paintable.
It comes with an open ceiling for natural light. I use LED circle lighting for photos. The clear plastic panels are optional for the windows to break up the light and give a natural lighting through the windows. The other wood panels can be used to cover the open ceiling or for a sliding door in the front. The entire room can be closed with the extra panels.
Regardless, these extra panels are not necessary for the functioning of the room. Thank you for being a customer. Please visit our store for other great items. The item "16 Dollhouse Luxury Victorian Style White House Room For 12 Doll by Eledoll" is in sale since Saturday, August 28, 2021.This item is in the category "Dolls & Bears\Dollhouse Miniatures\Dollhouses & Room Boxes". The seller is "eledollshop" and is located in Wixom, Michigan. This item can be shipped worldwide.