In engineering design, particularly in the use of computer-aided drafting and design, in the creation of 3D assemblies and multibody systems, the plural term "constraints" refers to demarcations of geometrical characteristics between two or more entities or solid modeling bodies; these delimiters are intentional in defining diverse properties of theoretical physical position and motion, or displacement. In addition, 2D sketches -including the ones used to create extrusions and solid bodies- can also be constrained.