Note: For less flexible baseboard, the best solution is to simply fill any gaps with caulk. Select a premium acrylic latex caulk ($3-plus per tube) that says “paintable” on the label. Force the caulk ...

Use a square or angle finder to determine if the corners are square. If not, determine if they are wider (obtuse) or tighter (acute) than 90 degrees. If the corner angle is wider, your miter angles ...