On a window sash’s frame, the stiles are the vertical pieces on the left and from the window pane. Like rails, they’ve grooves for placing the panes inside. Cross muntins extend from stile.
Like rails, stiles are also used to tag parts in furniture. They mention parts.
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Cross muntins operate from stile to stile.
Interiors with Attitude, LLC
Stiles are generally considerably wider than muntins and may be thinner than rails.