" Crown molding adds elegance and charm to any room. Making careful measurements is the secret to installing crown molding easily. Here's how. 1st, you need to choose a molding that's the right size and style for the room. You may want to bring home some samples to see how they look in place. Next, you need to measure the dimensions of the room to calculate the number of linear feet of crown molding you'll need to complete the project. Add at least 10% of the total length to allow for waste in practice cuts. There are 2 key tools you'll need to measure and install crown molding properly. 1st, you're going to need an accurate protractor to measure the angles of the wall. Most walls aren't square. The corner angles don't come out even so you need a protractor to measure the actual angles. Because of the accuracy needed, use a compound miter saw to cut the crown molding. The size of the saw that you'll need will depend on the width of the molding you're going to install. A 10-inch saw will usually cut up to a 5-inch wide molding. You'll need a bigger plate blade for a larger molding. There are different ways of setting up to cut molding. We will use an easy method called cutting in place. The molding is placed in the miter saw upside down against the fence. The fence of the compound saw represents the wall of the room. The top of the molding rests on the table, which represents the ceiling. The saw is fenced up, hold the molding so that the edges of the molding lie flat against the fence and the table. The advantage of this method is that you simply take the angle you measure with a protector. Let's say it's 90 degrees, and divide it in half to set the miter saw angle to make the cut. In this case, 45 degrees or half of 90. No further calculations are needed. Before you start cutting long lengths of molding, it's a good idea to do a practice cut to make sure you understand the process. Use 2 1-foot pieces of scrap molding to make a practice cut 1st. To cut the right side of an inside corner, you place the molding upside down with the bottom of the molding firmly against the fence stops. Set the miter for a left-hand 45-degree angle. Your molding will be on the left side with the correct angled cut on the end. To cut the left side of an inside corner, place the molding upside down with the bottom firmly against the fence stop. Set the miter to a right-hand 45-degree angle. Your molding is on the right side of the blade with the correct angled cut on the end. Try these 2 pieces in place against the corner and check the fit. The edges should fit tightly. If there's a crack, you may have to adjust the angle of the cut by a small fraction to get the 2 sides to fit tightly. For the left side of an outside corner, set the miter for a left-hand 45-degree cut with the bottom against the fence in position. The molding stock is placed upside down on the right-hand side of the blade. For the right side of an outside corner, set the miter angle for a right-hand 45-degree cut. The molding stock is placed upside down on the left-hand side of the blade. Once you understand the process, you can begin to cut the 1st inside corner, this time using your molding stock. Start by carefully measuring the length of the longest wall. Molding comes in 10-foot lengths so that the molding that you install on walls longer than 10 feet will be made up of more than 1 section. Using the protractor, carefully measure the angle where the walls meet. We measure an angle of 90 degrees. Half of that angle is 45 degrees so in this case, the 2 pieces of the crown molding will each have a 45-degree angle cut at the end. If the length of the wall is over 10 feet long, you'll need to space together 2 or more pieces of molding. To cut 2 ends of the molding together, we use an angled cut called a scarf. To make a scarf, set the miter angle to a 45-degree angle. Hold the molding to be cut flat against the fence and make a 45-degree angle cut on each end of the molding. Scarfs used to join lengths of molding together are held together and nailed on both sides of the scarf to form a tight joint. After sanding and painting, the joint is generally invisible. The molding is nailed to the joists with either a nail gun or a hammer and nail. Secure the molding to both the studs in the wall and the joists in the ceiling. You can find the location of the studs with a stud finder. Ceiling joists will be adjacent to the starts. If you choose to use a hammer and nails, 1st select a drill bit slightly smaller than the 8 or 10 penny finishing nail you're going to be using, depending on the size of your molding. Drill holes at an angle for each nail used to fasten the molding. This will prevent the molding from splitting when you drive the nails. Nail the molding in place and set the nail below the surface with the nail set. When the job is complete, putty the holes and paint the molding to match the ceiling. You'll find the room will have a new and refined look."