To show how they are used, it is best to go through an example of the cutting process.

Let’s say you have selected your starting point to be the right piece of an inside corner. The walls make a right angle (b = 90 degrees) and the molding has a spring angle of 38 degrees. You checked the corner and it is indeed very close to 90 degrees.

Using the Excel Spreadsheets for Calculating Angles, we find that the miter angle is 31.6° and the bevel angle is 33.9° . Set the saw to these values then place the molding on the saw table to the left of the blade with the bottom heel next to the fence. Is the miter angle to the right or left? To check this, hold R1 on top of the molding and index the miter angle. Remove the gauge, hold the part against the fence, and make the cut as close to the end of the molding as possible.

Now make a pencil mark on the bottom heel that corresponds to the length of the wall. Let’s assume the next corner is also a 90° , inside corner. Check the wall angle and verify M and B. For this corner our part is the left side piece. You notice that the bottom heel now needs to be towards you. So you have to rotate the part like a helicopter blade.

Place L1 on the part and line it up with the pencil mark. Move the part left or right until the blade lines up with the pencil mark. Make the cut! This is your first piece.

Notice how the gauges help to index M and B, as well as align the blade’s cutting path. For the next series of cuts it may be necessary to turn the crown around (like a helicopter blade), but as long as you keep track of the orientation (with the help of R1 and L1), it should become easier as you go along.

    When the molding makes a vertical turn, Type A-2 intersection:

This could be the case when the crown goes around a beam, or drops to a lower level, or maybe there is a lower section to the ceiling that has to be connected with a vertical wall. Note that the wall angle, b, is now the "ceiling angle". It is as if the ceiling and walls were rotated 90 degrees toward you and the flat wall has become the new ceiling. This also means that the "crown angle" has changed; it is now g instead of a.

I need to point out one difficulty with vertical turns:
Horizontal turns have the bottom foot (the edge that is against the wall) from corner to corner. It is the edge that you mark with the wall length. That is not the case with vertical turns. The foot that is in contact with the wall will stop short of the corner for inside turns and go beyond for outside turns. The amount is Offset 2 as shown above.
So how do you mark the pieces and cut them to the correct length? You can calculate the amount for the Offset 2, or hold two short pieces of molding in place and draw two pencil marks on the wall. The length of the horizontal pieces can now be re-measured to these points.

For wide molding, I will make a plywood template with the correct height and width of the installed part. This gauge can be used to mark the walls at several places, especially where it involves a vertical turn. Note that the outside contour is not important.

The new rules for vertical turns are as follows:

For inside corners:

• The left part is placed to the left, with top heel next to the fence and miter setting to the left.
• The right part is also placed to the left, but the bottom heel is next to the fence and the miter setting to the right.

For outside corners:

• The left part is to the right, with the bottom heel next to the fence and miter setting to the right.

• The right part is to the right, with top heel next to the fence and miter setting to the left

Be sure to calculate the new bevel and miter angles using the spreadsheet. It already accounts for the change in crown angle for both inside and outside corners.

   Advantages of Method 2 include:

• Improved accuracy
• Secure and safe way to cut parts.
• Versatile, can be used for most wall-ceiling intersections.

            Disadvantages include:

• Requires setting both miter and bevel angles
• Without templates it is difficult to visualize how the part is positioned on the saw bed.

Cutting Crown Molding on the Table Saw

There are occasions when the crown molding it too wide or the miter angle is too large for a compound miter saw. That is when you should use a table saw or cut the material by hand. The same applies when you have to cut flat stock that has a bevel angle larger than about 45° . For example, I have installed chair rail and wall frame molding along a stairway wall where the miter angles were more than 50º. These were cut on the table saw with a special fixture to hold them securely on the sliding miter table.
I discuss this in more detail in Part 3 --  Crown Molding on Vaulted Ceilings.    

  Method 3:. Coping the Joint

Coping refers to cutting material with a coping saw. This is a small, hand held saw with a thin blade for cutting intricate pieces of plywood or thin boards. This saw can be used to cut sections of molding so they can be joined in corners. Coping can be used on simple sections of straight molding as well as on crown. However, it is only good for inside corners. Outside corners still require a mitered joint.

The technique basically involves keeping one piece straight while cutting the mating part such that it fits the contour of the straight piece. To prepare the second piece you first have to cut it per Method 1 at half the wall angle. This exposes the profile.
Using the coping saw cut away the bevel part as shown above. For a right wall angle you would cope away  the bevel part at 90 degrees right along the sharp exposed edge. In fact, you could cut a bit more than 90 degrees to provide additional clearance. The part should be clamped as shown above or on the edge of a work table using a clamp of some sort. To mark the edge more clearly you might rub a soft pencil point along the exposed edge. Use a file to clean up the edge and make a trial fit to a scrap piece of the same molding. You will want a close fit to minimize the gap to be filled.

Simple? Well, yes and no. It really takes some practice to do it without wasting a good part. Commercial installers like this method for several reasons:

1. Only one end needs to be coped.
2. Some of the coping can be done in the shop before going to the job site. 
3. Some claim that the joint is more forgiving to expansion or contraction after the installation. I have my doubts this is really true.
4. It is the best way to handle wide crown molding (saw limitations).

I still would recommend that the average person use methods 1 and 2 above. There are times, however, when coping becomes in handy tool. Here is one example:

The ceiling in one room has crown all around. One side drops down about six inches to another level - a family room. The intersection becomes complicated. Three pieces of crown meet at right angles. Two can be joined as discussed above, but the third needs to be fitted to follow the contour of that joint. Here is what it looks like: The top right piece was coped to join the other two.

4. Installation of Crown Molding

First things to do:

• Make a diagram of the floor plan of the room. Number each segment and measure the lengths of each wall segment as well as the angle the walls make at each intersection. If any wall length is more than sixteen feet you need to make a splice; show the best place on the diagram.
• Determine how you can best cut the pieces from the standard sixteen foot lengths.
• Order the material along with some extra for an "oops" or two. Mark each with the segment(s) number using a light pencil mark.
  

Next things to do:

• Get help, don’t try to install crown by yourself. 
• Get the right tools. Buy, borrow or rent a compressor and air gun with two inch "nails". Installing molding by using a hammer and two inch finishing nails is too cumbersome, time consuming and hard on your knuckles. 
• Check if you can find any utility lines such as electrical or water lines imbedded in the walls. The chances of driving a nail into a line are extremely small. However, at one time I did manage to drive a nail through a plastic water line. If I had checked the other side of the wall, I would have realized there were two lines going into the wall from a water heater. The water lines ran up and through the attic. The consequences were expensive.
• Find the wall studs and mark the wall and ceiling where you find them. These are the best places to nail the molding. You can use a stud finder or simply drive a nail through the wallboard right underneath where the molding will cover the hole. Keep in mind that most wall studs are on 16 inch centers. Also, you will find that wall outlets are installed next to a stud. Ceiling rafters are usually spaced 24 or 16 inches, depending on whether it is a one or two story home. But rafters run only in one direction and you will encounter many runs without ceiling support.

For wide or very flexible molding, consider using wooden nailing blocks on the backside of the molding. The sketch in Part 4 Special Fixtures and Tools  shows how these blocks can be cut from a 2x4.  The blocks can be spaced about 24 to 32 inches apart and should be nailed to the 2x4 braces at the top of the wall or the wall studs. Put a small pencil mark on the wall below them so you can see where they are located when holding the molding in place.

• Mark the walls to show where the foot of the molding should be. This helps to align the parts before you nail them in place. Crown molding sixteen feet long is like a big noodle and it is easy to slightly rotate it and misalign it at the corners Some installers strike a line all along the wall, but I find that marking the wall in several spots (using a pencil and a small guide block) is good enough. If you are building up the crown using flat molding plus crown, you don’t need a pencil reference line; the flat molding will be a better line to follow. However, make sure the first parts are exactly where you want them.

Note: If you have never installed crown, start with two short sections of wall with inside corners. If you make a mistake now it only involves short pieces. With your helper, re-measure the wall length close to the top.
I find that to get a good measurement, it is better to use a "witch-rod", a piece of dowel or flat stock of known length (ten inches is good). Hold the dowel to the end of the wall, measure up to its end and add 10 inches to the value. This is better than flexing the tape around the corner or adding the width of the tape measure. Check the corner angle (if you have a wall-angle-gauge) and jot these values down on the sketch of the room.

When I am ready to start, I like to go around the room in a clockwise direction. If the room has mostly inside, 90° corners, I will precut the end of each section as a right side piece. Now I mark the wall length on the bottom foot and use template L1 for the second cut. This template is better for lining up the blade with the pencil mark.

Cut the first piece of molding as described in the previous section and hold it in place. Line up the bottom foot with the marks on the wall. If it makes good contact in the corners, tack it in place with a few nails. Now measure the next wall, cut its molding and see how the two pieces come together. If there is a problem, you can still remove the first piece that was just tacked in place. If all looks good, tack the second piece in place with a couple nails again using the pencil marks on the walls for alignment.

Continue around the room until you encounter an outside corner. If the crown has an inside corner at the other end, cut that first. Hold the part up to the wall and mark the wall heel right where the wall stops and goes around the corner. Do the same with the part that will mate it. Measure the corner angle, calculate, and set the saw parameters. 

It has been my experience that outside corners are never 90 degrees. A metal edging is used when the walls are taped. This is then filled with joint compound, resulting in a bulge and an angle that is usually about 87 degrees.

Now you are ready to cut the outside corner, but be sure that the heel that goes against the ceiling is now longer than the wall heel! When you have a perfect fit apply some carpenters glue to the joint and nail it in place. The glue helps to prevent the joint from separating later on.

If the inside corners are not perfect, don’t worry. That’s why they make carpenters caulk and wood putty. Putty is good for filling nail holes (some may need to be set with a punch), but it dries hard and brittle. Silicone based caulk is more flexible and better for filling gaps in the corners and along the top and bottom of the crown. I prefer the water based type for both. It is easy to clean before it sets and can be painted. One tip: run a small beat all along the ceiling right from the caulking gun, then use a finger to wipe and smooth the fillet. A damp rag cleans up the excess.

Stand back and admire your handy work!     

Some examples: 

The old cliche "A picture is worth a thousand words" is very apropos when it comes to crown molding. The following photos were taken during and after installing a combination of crown and base molding in a kitchen with several soffits. There were a total of ten inside corners and eight outside corners. To soften the sharp projections of the crown, it was decided to cut the corners with a 45 degree section as shown below. Notice again that the crown is installed "up-side-down".
The pictures were taken during and after the installation.