The only true outsider of the bunch, It will fit nowhere inside your buildings and unbalance the perfect proportions of your structures. It can barely stand by itself. However if you plan to use the Pixels to create a bi dimensionnal psychedelic fractal maze, or just quickly fill a gap in a defensive line, It will literally become your best friend, and will be secured just by pushing it against a cube or even connect to it via rods.
The Cube