This might be useful for a DIY newbie, but any pros thinking it's something a tool junkie needs to hang trim- forget it. Just another solution looking for a problem.

This is a handy tool that takes a bit of getting used to.

Pros
You put it to the casement much like a speed square
It automatically gives you a 5/16 reveal
You can drag it along the casement to scribe your line, if you like
Is handy to push molding against to nail
Grooves for automatic length measurement

Con
The slots for hooking rule too small for Stanley Fat Max

Use it to do the trim on the inside of a whole house. Cut the time in half. Very few recuts with this.

I bought 1 because I was going to be installing new trim on all the doors in my house, and then got a second from my wife for christmas. It was actually a good thing. I have the first one nailed down on a lond piece of 8" wide Pine which I use to measure the length of the cut that I need. The second one I carry around with me and use to mark the door jam for measuring, and then to line up the trim for install. I reccomend using a nail gun instead of a hammer because I found you need a third hand when trying to use the hammer and the tool.

All my reveals were perfect, and the miter cuts were right on.

The main diffrence between the metal and plastic is that the metal tool is 1/4" reveal and the plastic is 3/16" reveal. I thought 1/4" is a bit much, but the 3/16" looks perfect. For those worried about using a plastic tool, it has held up perfect for this project, and will be fine when I go to replace all the trim when I replace the windows.

This is a great tool, and really sped up the time it took to install the trim.

It does just what it is designed for - assists in laying out measurements for molding and trim. It is fairly easy to use, once you get the hang of it. The directions are somewhat vague, so it took a bit of practice to determine the best way to mark the cut lines on molding. Otherwise a real handy product that easily fits in your tool belt.