The spacer in a window is located along the edges of the glass panes within a double-glazed unit. It is positioned between the two glass panes and runs around the perimeter of the window.
When you look at a double-glazed window from the side or edge, you will see the spacer as a thin strip that separates the glass panes. It creates a sealed space between the panes, which is typically filled with air or a gas for insulation purposes.