Not too happy with you using autism to call someone dumb, but I'll leave this up assuming it was just a one-off.
Definition of sash for Students. 1  1 : a frame for a pane of glass in a door or window. 2  2 : the movable part of a window.
curtain. n. 1. a piece of material that can be drawn across an opening or window, to shut out light or to provide privacy. 2. a barrier to vision, access, or communication: a curtain of secrecy. 3. (Theatre) a hanging cloth or similar barrier for concealing all or part of a theatre stage from the audience.