When installing baseboards, crown molding ("moulding") and chair rails, it's tempting to cut 45-degree miters at the corners and hope for a sure fit. The problem is that most walls aren't square. Joining two 45-cut molding pieces may give you a square joint, but a square joint may not work for your crazy corner. In fact, it seems like every wall is just a "hair" out of square. This problem could be due to a framing error or a buildup of drywall compound in the corner. But even a perfect miter joint can develop gaps when the wood dries and contracts in winter. Don't cut corners when you cut corners and watch this DIY video tutorial before starting your molding project.