Need help w/Sketchup

[Anthony Welch]

I'm making a shadow box and trying to draw it out in Sketchup. I've got my faceframes with a 45 on the
outside and a curve on the inside of these rails. Now I need to 45 miter the ends of these. I can't, for the
life of me figure it out. I've tried to find tutorials on U Tube. I'd really like to find a video w/audio on how to
do this. I don't want someone to do it for me, as I want to learn how myself. If the protractor tool is used,
I'm not familiar on how it works.

Just to let you know I can miter a rectangle, but not these with curve and angles on both edges.

Thanks
Anthony