mitre hfss

I was just wondering if anyone could tell me how I can add mitres to my transmission lines in HFSS. Preferrably I'd like it for 3D rectangles, although I can live with the 2D. I tried just making one from the polygon function, but it doesn't seem to work. Any help/insight would be greatly appreciated.

hi
have you ever tried boolean operations?
draw your normal line.
then draw the part that is to be deleted from it to form a mitre.
select both forms <<S>>
then >> boolean oper >> subtract

Hey thanks a lot, I can do this in 2D fairly proficiently now, but I honestly need this for a 3D rectangle/box. I tried making a 3D object using the line function, but it would not connect the surfaces and subtract properly. Any suggestions?

Added after 8 minutes:

Scratch that, got it to work 3D. But do you know if there's anyway to make it based off an equation rather than have to go through every mitre if something needs to be changed?

make your line, drew box, rotate the box at 45 deg, sub the box from the line