Primary Members

You can create primary members with these methods:
Path Segment Creates a member along a sketch entity. Select one or more sketch entities (similar to weldments). You can also select model edges for path segments.
Reference Plane Creates a member along the intersection of two or more planes.
Point and Length Creates a member originating at a point and extending for a specified length. Select one or more points and specify a length.
On Face Creates a member along the intersection of a face or surface, and a plane.