Surface

Surfaces refer to the six sides of a part, each of which can be changed through its corresponding surface property (e.g. TopSurface). Surfaces are represented by the SurfaceType enum, which currently has ten kinds of surfaces. Each surface type exhibits different behaviors when interacting with each other, but primarily functions as a decoration.
Similar to materials, even though some surface types appear three-dimensional, none of them have true depth. Surfaces only visually appear and behave on parts with the plastic material applied. If all the surfaces on a part are smooth, then the "surfaces" section on the corresponding part's properties menu is hidden.
In Properties, if all of the surfaces are Smooth surfaces (which is the default for parts), the category for surface properties will be hidden. To make the category visible again, a surface property must be changed through Lua, such as via the command bar.
==List of surfaces==
;Studs
:Studs are akin to the top surfaces of Lego bricks, and instead are rectangular.
;Inlet
:Inlets are akin to the bottom surfaces of a Lego brick. Inlets will only connect to stud, weld, and universal surfaces.
;Smooth
:Smooth is the default surface type, only connecting to weld surfaces. Its deprecated subtype, SmoothNoOutlines, is the same as smooth except for its removal of the also deprecated outlines.
;Weld
:Welds have X's on them, and can hold onto any block it is touching without being anchored.
;Glue
:Glue is a deprecated surface type that resembled clear, colorless, squirted-on glue. It originally could only hold on to spheres. If somehow selected in Roblox Studio, it would turn into a weld.
:Glue when applyed with force, it would break.
;Universal
:Universal is a checkered combination of studs and inlets. It can connect to inlets and studs, hence its name.
;Hinge
:Hinges are non-automatic motors. It will only spin by gravity.
;Motor
:Motors are automatic. If you connect an unanchored brick to a motor surface, it will spin automatically.
==Deprecation==
While Roblox does not plan to remove surfaces, they have removed much of its functionality. This is due to their engine having many better, more in-depth alternatives such as constraints, as well as the system of surface interactions being confusing to newer developers. 
As such, on August 19, 2019, the ability to weld the surfaces of spheres and the curved surfaces of cylinders was removed, as well as some of the functionality of surface joining. On August 13, 2020, the "surfaces" tool was removed from studio, and some of the behaviors of hinges and motors were also removed. Applying surfaces is still available in plugins such as F3X.
==Trivia==
 
*There used to be a bug where surfaces in studio were visible in non-plastic materials, even though they disappear in the normal Roblox program. This was fixed on August 19, 2019.
==References==
Category:Experience features
Category:Game development