Re: How to make the upper parts of the curtain wall like an arch Hello, you can access the roof cut command from the tools tab. When you click on the command, a floating toolbar will appear, select the new trim group from this section, and follow the instructions on the taskbar below, in order; 1-Select the roof you will trim and press the right mouse button for the next step. 2-Select the objects you want to trim and press the right mouse button for the next step. 3-A tab will appear, choose the ones that suit you and click all.