Wall hung shadow boxes can vary much in size. From an eighteen wide shadowbox to a six feet wide there is much difference when devising how to install them. Small shadow boxes should be leveled against the wall and then screwed carefully to the studs of the same wall. The screws or nails should not be visible but instead drilled inside the top and bottom cabinets. Large size wall mounted shadow boxes should be installed by a professional or handyman. Their size and weight will require a bit of studying. When installed up and against a wall not only do they need to be attached but base support is absolutely necessary. The mere weight of the wall hung shadow box will create a lot of stress of the structure of the glass case and may damage it. By using metal L brackets under the base of the shadow box one will reduce this pressure and avoid the shadow box falling off. Of course each situation is different which is why a good handyman is highly recommended.