This Enum appears to be obsolete as all of these are present in the SurfaceType Enum.
No surface constraint.
Makes the side appear with a yellow hinge. Any part connected to this hinge will stick to the side and rotate using physics
Functions identically to a motor. It may have functioned differently in the past, but that functionality no longer seems to exist.
Acts the same as a Hinge, but has a grey ring around it and automatically rotates any part connected to it.