Uberspecification

Uberspecification is where a block's variant value is set beyond any variant with textures, making it appear as a question mark encased in a circle, with an overlay stating the ID and Variation of the block.

Until February 9th, the texture was the same as the Metal Block, and could be potentially used for troll levels.

Something that may appear to be uberspecification, but really isn't, is breaktexture.

Uberspecification used to be useful for making hidden blocks, but now that style-changer breaktexture exists you can just set the texture of a block to blank, or anything else, in the middle of a normal-looking level. Uberspecification isn't necessary to make troll levels anymore.