Create a new surface by extending it to meet the edge of another object or by specifying an extension length.

There are two types of extend surfaces: merge and append. The merge surface is a continuation of the surface with no seam. The append surface extends the surface by adding a second surface with a seam. Because it creates a seam, append surfaces have continuity and bulge magnitude properties.

For both surface types, use the Properties palette to change the length or to derive the length from a mathematical expression.