DiagonalObject
From SimsWiki
==Diagonal Objects==
These are autonomous objects (i.e. curtains, doors, windows) that are used by the Sims 2. When an object is placed on a diagonal wall, it automatically converts to hang on the diagonal wall. Instead of the normal object,(probably to allow for the fact that a diagonal wall is wider than a standard grid aligned wall.
These objects share the textures and catalog entry files with the Grid Aligned or "normal" object.