MakeHole in a cylinder (normal to the surface)

Hey, Im a very beginner to Rhino. I need to have a tower with windows. I’ve got 2D elevations of the towers - and I project the windows on the cylinder (tower). Now, when I try command makehole on the towers with those projected windows it doesnt work. Anyone may help? What am I doing wrong? Is there any easier way to do so? Thanks for help!

Usually, you can use the Trim command in one of the non-perspective views, even if the surface and the curve do not overlap.
MakeHole requires a planar curve if I’m not mistaken.

Thank you for the answer, I tried Split (as I dont want to delete the surface of windows) but when I have the curve on the surface of the cylinder I can only push it inward along XY directions, cannot pull it inward to the centre axis of the cylinder…

I’m assuming that the split worked…

To get the window surface inwards to the center of the cylinder, you can use OffsetSrf on the window surface.

It did work! Thanks a looot!