How do you make a mitred corner? I'm working on making a triple glazing corner sample, and I want to be able to mitre the profile at 45 degrees so I can duplicate it, rotate it and join them to make an elbow. I've muddled through making the profile, but now I'm stuck on how to get that 45 degree angle.

I've had a look around Google, perhaps I'm not phrasing my question correctly but I cant find any answers. I did try creating a cube to use as a sort of cutting form, but Blender wouldn't let me use a Boolean modifier to do it. Any thoughts?

Thank you!

What I'm trying to achieve:



What I have at the moment:
I would suggest using the shear tool to do this.

With the vertices at one end selected go into the side view (shear deforms based on the view) &#9096; Ctrl&#9095; Alt&#8679; ShiftS and then enter a value of 1 (or -1) to get a 45 degree angle. If your pivot point is set to median then you may need to move the edge sideways to re-align it or you can position the 3D cursor and set the pivot point before shearing.