This is a 'beam' pendant phase 1. These are made out of scrap pieces of the baseboard, WM 620, we used throughout our house. The base is flipped upside down and mounted as shown up against the ceiling.

These had to be dimensioned such that the 'front' (the side with the big notch in it) would fit OVER the beam and still have enough space on either side of the beam for a piece of WM 54 crown cut at 12 degrees (the angle of our cathedral ceiling) to fit. The front dimension ended up being 7 1/8 inches wide.

The 'sides' are dimensioned such that the larger 'perimeter' crown, WM 320, could land on it. The challenging part of figuring out these dimensions is that with a cathedral ceiling, you wind up with 'upper' and 'lower' pendants. At the outside wall of the room the angle from wall to ceiling is more than 90 degrees, an obtuse angle. And on the inside walls the angle is less than 90, an acute angle.

All of which leads to changes in how the 'perimeter' crown lands at the sides of the pendants. This will effect how 'tall' the pendants are. This is something you have to look out for when you're designing things. Make sure the 'perimeter' crown will always 'land' on the sides of the pendants irregardless of whether you are at an outside or inside wall.

The clamps in the photo are made by the Collins Tool Company (www.collinstool.com) and are EXTREMELY handy for all of these miter joints. I used Titebond molding & trim glue for all of the joints because it dries clear and is less noticeable if I mess up a joint than regular yellow glue.