I have a need to replace a few clapboards on a dormer. The roof the dormer sit in is 10:12, or has a 40 degree slope, relative to the horizontal. The clapboards on the side sticking out of the roof are horizontal (5" or so wide cedar) and to "fit" up against the roof one end has to have a 40 degree rise.

My power miter saw (any miter saw in my experience) is able to go 45 degrees left or rigth from a verticle cut, thus it can not cut a 50 degree (off the verticle) cut to make the end of the clapboard expose a 40 degree rise from the horizontal.

I have played around on paper and just don't see a way short of blocking the clapboard so it comes into the miter cut at a 5 degree angle - suggestions?

Yes, I can mark a 50 degree cut line and cut it with a hand saw, but gee - seems something like this should be doable on a miter saw.

Besides, my 10:12 roof is rather steep, if it were a 8:12, say the angle of the rise would be approximately 34 degrees and thus the cut I need to make would be 56 degrees off the vertical.

Thanks,