paper block clamp onto plank

I may use paper to draw designs on, but reading it while using the laptop, it gets in my way. So i put yet another thing to clamp onto the plank.

Works pretty well for me, though i do have to push the paper high enough so it doesnt slide loose too easily.(the paper block has to be thick enough too.) I also needed to use rubber bands to grip it better. None of the tape i had had enough grip, though some did better than the plastic.

NOTE: the version i tested had some slicing issue and i added some stuff since it, but i inspected things, so probably it is fine. (feedback appreciated)

As usual, development versions at github.