Yes, it does work.
1. In the plan view, draw the marquee so it cuts the rafters where you want them cut .
2. View this in 3D window
3. Look at it in the orthagonal view mode from the top (as you will place the resulting object)
$. Save 3D window as a new library object.
the new library object is on the right side.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"