If I understand correctly, you want to do that ?
If yes, you can use the default object 'arch'.
if no, you must create two walls* which will export in obj format.
You import again the new object and when you see the green arrows, click on up right frame (front view) and then with the mouse and key shift click on the down green Arrow to have 90° and click enter...
You'll have your half arch, see the joined file below.
(*) First wall : standard
Second wall : same than first but 'arc extent' = 90° and joins the twice.
----------------------------------------
Half arch.obj
(12572 bytes)
(Download count: 2176)
----------------------------------------
Evil progresses when good people do nothing!
---
SH3D 7.1 and nothing else - W11 64b in 4K
