In Computer-Aided Design (CAD), a sketch is a 2D profile or cross-section that forms the basis for creating 3D features in a model. Sketches are the foundation of most CAD models, providing the basic shapes and geometry that are used to create solid features like extrusions, revolves, sweeps, and lofts.

Sketches are typically created on a 2D plane, using a variety of sketch tools and commands. Most CAD software packages provide a dedicated sketching environment, with tools for creating lines, arcs, circles, splines, and other geometric shapes.

When creating a sketch, designers typically start by defining the basic shape and proportions of the desired feature, using dimensions and constraints to control the size and position of the sketch elements. Dimensions specify the length, angle, or distance between sketch elements, while constraints define the relationships between elements, such as parallelism, perpendicularity, or tangency.

Once the basic shape of the sketch is defined, designers can add additional details and refinements, such as fillets, chamfers, or holes. These details can be added directly to the sketch, or can be created as separate sketch elements and then added to the main sketch using boolean operations like union, subtract, or intersect.

Sketches are a critical component of parametric modeling, where the geometry of a model is defined by parameters and relationships. By creating a parametric sketch with dimensions and constraints, designers can easily modify and update the model by changing the values of the sketch parameters, without having to recreate the entire sketch or feature.

Sketches are also used to create reference geometry for other features and operations, such as paths for sweeps or guide curves for lofts. By creating accurate and well-defined sketches, designers can ensure that their models are precise, consistent, and easy to modify and update.

Most CAD software packages provide a range of tools and options for creating and editing sketches, including grid and snap tools, sketch constraints, and sketch pattern tools. These tools allow designers to quickly