Raised square goza mats can be used to place add-ons above "floor" level. If the add-on is multi-tile, you need a goza for each tile to "support" the complete graphic of the add-on (for example - arcane circles need a 3X3 goza platform to support them fully). All the gozas must be at the same height when you place the add-on. Once you have done that, you can remove the gozas...however when you remove that "support" and for example, drop another item on top of your raised add-on, that can cause the add-on to sink in one place, and it is "broken" - you can also do this by using the deco tool on any one piece of the add-on. If you chopped it with an axe in this "broken" state, only the tile where you chopped would be deleted and your add-on would be destroyed, and no longer re-deedable. You would have to chop each remaining section to remove it completely from your house. If you use the deco tool to bring every piece of the add-on back to the same level, it is no longer "broken" and you can axe, and get it back in deed form.
By going on what people discovered by accident, a lot of the fun deco techniques we play around with now involve intentionally breaking the add-on to get just a certain piece where we want it.
-Skylark