mitre joint

 From:  Michael Gibson
5407.7 In reply to 5407.6 
Attached here is an example for doing 1/3 of your shape by a sweep - note I've slightly modified your shape here so don't use it directly.

But here you can see 2 lines joined for the path, and then the profile is 1/2 of your end shapes.

You can select that profile then run Construct > Sweep, select the 2-line path for the rail and that will generate I think 1/3 of the shape that you want, then you need similar things set up for the other 3 zones and then you can boolean union the results together.

Note that the sweep profile should be perpendicular to the line path, not slanted - the ends of your original shape are slanted, you would probably introduce the slant later on by slicing off the ends.

- Michael