A sketch without constraints is just a pretty picture. A sketch with constraints is an intelligent model.

Catia divides constraints into two types: Geometrical (shape) and Dimensional (size).

| Tool | Icon Behavior | Key Use Case | |------|---------------|---------------| | Profile | Continuous line/arc chain | Roughing out closed contours | | Rectangle | Various types (centered, 3-point, parallelogram) | Base flanges, mounting pads | | Circle | Center & radius, three-point, tangent arcs | Holes, shafts, fillets | | Spline | Interpolated smooth curve | Aerodynamic or freeform boundaries | | Ellipse | Center + major/minor axes | Specific cutout shapes | | Line & Infinite Line | Single segments or construction lines | Reference geometry, symmetry axes |

In CATIA V5, the Sketcher is the foundation of 3D modeling. It is a 2D environment where you define the profiles and cross-sections that are later extruded, revolved, or swept into 3D solid parts. A well-constrained sketch is the key to a stable parametric model.

Accessing the Sketcher: