Here's a patent-pending (by yours truly) idea . . . .
One of the limitations with the Domino is mortising narrow pieces such as rail and styles. The two registering pins are great when using wider boards, but are unusable with narrower 2 to 3-inch boards. I've tried the approach of aligning the rail and style precisely by hand and drawing a line across each piece and then mortising using the plastic sight gauge line, but even after calibrating that set-up, I find that once the entire face frame is assembled, there is an ever-so-small 1/32ish error. I am a pretty careful technician, so at this point I don't think it is my technique as much as it is a limitation of the tool.
But I think I have a workable and inexpensive solution that Dominoites may appreciate!
I had a package of smaller earth magnets lying around. I put three of them against the retracting registering pin to force the Domino to position its bit close to the center of the rail end (there is no need for it to be precisely centered). I made my cut, then moved the same three earth magnets to the other registering pin and made my cut on the style. The result is a perfectly matched joint, and done in a matter of seconds. No more tedious and error-prone measuring and line drawing.
I used a set of magnets available at my local Woodcraft store. Larger ones may work better. If I needed to vary the distance of the mortise cut from the edge, I need only add another small magnet.
The photos below tell the story:
Treasure Island FL