Basically i downloaded the GKWare curved stair plugin and i created the stairs i needed but now i am struggling with cutting them through the ceiling/bottom of the first floor. As you can see in the first two gyazo links i attempted to make vertical lines on the edges of the stairs to create the cutout shape on the first floor so i could remove it. How do i go about cutting this shape out? i would usually pull it upwards and remove the lines but as you can see in the 3rd and 4th links the whole floor gets selected and not just the curved shape what have i done wrong guys? I have never had to do something like this before, especially with A complicated shape so im really stuck!