This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/frL1R0cvBQH

This is a gothic window designed to be used with 1/2 inch insulation foam for wargaming terrain walls and ruins.

Use the window insert to trace the hole cut. Cut it a liitle smaller, you can always enlarge if needed. The foam was carved with a ballpoint pen, paint with miniatures paint.