To follow up on my original post, I should add some thoughts. While not taking away from Mike's idea, safety must be your first concern. This jig is a good starting point yet it could stand a little tweaking. For anyone considering making a jig like this, especially those less-experienced doing flat work, there are two important considerations other than those raised above:
1. The clamp extension passing over the blade is a safety concern.
As pen makers, we're not likely to raise the blade up that high, but it's important
to be especially cognizant of the possibility of hitting the clamp arm with the blade.
2. A sled with a single runner requires you to make that runner absolutely spot on.
Any slop will make the jig frustrating to use.
If you make a single-runner sled, use a tight, straight-grained stable wood like unfigured hard maple or even something like purple heart or IPE and make it absolutely tight.
I make my runners a hair too big and then plane or scrape to just fit. When they're hard to push dry, I buff 'em with wax and see if they slide. If they stick, I scrape a hair more til they just barely slide. You don't want any side-to-side movement.
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