Close Corner, Outer Edges Flush
Sheet Metal > Change length > Corner/Mitre > Mode: Close corner, closed 
> Joint: Outer edge, flush 
If you choose the mode Close corner, closed and the joint type Outer edge, flush, each sheet will be lengthened to the outer edge of the other sheet. This also applies to the bend zones and milling edge zones.
Proceed as follows:
- On each flange, select an edge of the front side, or, with a right-click, the right-click, the longitudinal edges.
(1) Front edge
(2) Front edge
(3) Lengthened (or shortened) to outer edges of sheets
