Outlines

Outlines are a feature of ROBLOX parts that allows them to be drawn with a pixel-shaded outline on each edge. In August of 2013, it was announced on the ROBLOX Blog, that Outlines would have an option to be disabled. The color of these outlines are fixed at black, but can be disabled in two ways:
 * Setting the Outlines property of Lighting to false, which disables all outlines in a place.
 * Setting the SurfaceType on one of a part's Surfaces to SmoothNoOutline, which disables the outlines on the four edges adjacent to the specified Surface.