Three clicks, one pergola

In the studio a pergola is drawn by its outline on the ground. Two clicks set the back edge, the side against the house, and a third sets the depth. A free shape works the same way: click four corners and the posts go on the corners you drew.

The size snaps to the nearest size the model is sold in, and a notice tells you it did, so you know where the pergola differs from what you drew. To change the shape later, open Modify shape and drag a corner: the post goes with it. Drawing works in the 3D view, the photo view and the plan view.

This is how salespeople already work on site: they measure a terrace by its corners. Drawing those corners in the scene is faster than placing a default pergola and dragging its handles until it fits, and it starts from the same corners the salesperson measured.