Yamsan,
Please add your archicad version and OS to your profile.
The skylights may not be cutting holes in the roofs Perpendicular or vertical to your roof. See
here
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"