While working with families in the Family Editor, you can create a blend form by blending from one 2D shape to the other and adjusting the height and vertices.
This video demonstrates the following:
A blend is a form created when two 2D shapes, or profiles, are defined a specific distance from each other. The resulting 3D form is created by blending from one 2D shape to the other 2D shape over the distance between them. To create a blend, select the blend command. You are placed in the Sketch mode.
Select a tool from the Draw menu to draw a closed-loop sketch for the base of the blend. Once the base sketch is complete, click Edit Top on the Mode panel of the contextual tab. Now, the second 2D shape of the blend can be sketched. Use the First End and Second End parameters in the Properties palette to establish a distance between the 2 profile shapes used for the top and bottom of the blend form. Finish the sketch to create the blend.
The height of the resulting form can be controlled with grips when selected. Edges and vertices of the blend can be controlled by selecting the form and editing the top or bottom shape. The sketch can be recreated or altered or the Edit Vertices control can be selected to change how the vertices of the upper and lower shapes are connected. The vertices' connection can be rotated or additional vertices connected.
Once the modifications are complete, click Finish to create the form. The material and visibility parameters of the form can be set from the Properties palette.