Which type of sculpture projects from a flat background but remains attached to it?

A relief sculpture is one that projects outward from a flat background surface while remaining physically attached to it. The forms are raised (or sometimes recessed) from the backing plane, so the sculpture is meant to be viewed primarily from the front. Relief comes in degrees: low relief (bas-relief) barely projects, while high relief (alto-relief) projects significantly from the surface.

A full-round (or free-standing) sculpture is completely detached from any background and can be viewed from all sides. "Subtractive" describes a process (removing material) rather than a type of sculpture. "Assembly" (or assemblage) refers to sculpture made by joining together separate found objects, not sculpture attached to a background surface.