No KO

Box is the common term given to a Stage Builder stage which is completely enclosed. It is impossible to get knocked out of a box. To build a box, simply build a stage-builder stage and make the walls and bottoms of the stage sealed by blocks. Then seal the "top" of the box with falling blocks. The fighters start and spawn at the top of the stage, it is possible to get KO'd there. The only other way is if you are on a high damage. Since Boxes prevent most usual KOs, they are often used for Stamina matches. Boxes can be modified for all sorts of matchups, including varied heights to negate projectiles or making it small to prevent camping. Other things such as placing conveyor belts and moving platforms can be added, making aerial matches more dominant. This is only limited by the limitations of the Stage Builder

Partial Box

When a Stage Builder stage has some properties of a box, but is not fully enclosed, it creates an odd gameplay. KO's are not impossible, but rare. For example, a partial box may have a similar design of a full box, but has a small opening. Also, it may have the top layer open, but the stage is extra large, so the players cannot jump out. This removal of the side and floor blast lines causes characters with meteor smashes to have a disadvantage, and characters who have upward knockback attacks are at an advantage.

Exceptions

Some Final Smashes cause a player to go to the top of the screen, such as Olimar's. In this case, it is possible to 'escape' the box. The escaped fighter can then get SDed.