how to create unusually shaped polygon in altium

[MrSun]

how to create unusually shaped polygon in altium .
e.g.
the polygon around the pcb in this board.it's a screenshot from Phil's Lab,here is the video link:How To Get Your PCB Manufactured & Assembled - Phil's Lab #94

[qdrives]

You can place some tracks and arcs to create one corner.
Select them, Tools -> Convert -> Create polygon from selected primitives.
Copy the polygon and mirror it for paste (X or Y).

[MrSun]

thank you very much.