Draw a keyhole peninsula
- Draw a rectangle shape.
- Click on one of the long edges and select Bump Out Arc.
- Select a Depth and Width and choose left (or right).
- Click on the opposite long edge and create another Bump Out Arc with the same Depth and Width but choose right (or left).
- Click on the short end and choose Full Radius.
- Enter a Depth.
- You will likely need to tinker with the measurements until you get the shape right.