A. Doug Price, vice president of marketing at Norandex-Reynolds, a vinyl siding manufacturer, responds: An inside corner piece bent backwards may look unattractive. Depending on the trim configuration, it may also lack pockets deep enough to accommodate the expansion of the siding. The best solution is to use a 45-degree bay corner post, a type of trim piece available from some siding manufacturers.
Unfortunately, 45-degree corner posts are usually available in a limited number of colors. If you can’t locate the right type of vinyl trim, you can always install a piece of wood trim and wrap it with aluminum trim coil in a color that matches the siding or trim.
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