Working on my Kossel can sometimes be frustrating, especially when I want to adjust the bed height and leveling at the beginning of a print, after downloading and printing every bed leveler / mount design that I could find and after none of them working I finally decided to design my own in Tinker Cad.
UPDATE: This design is depreciated, it allowed for too much bed movement which caused layer misalignment in larger prints, I designed a more stable / simplified version, check out at: http://www.thingiverse.com/thing:2092046
It's made up of 4 parts, the thumb screw, the mount base, the shafted bed mount and the top clip to lock the bed into place. You will need 3x M3x30 scews, 3x Springs and 3x M3 nuts as well as a T-slot nut and M3 screw to mount it to your 20x20 extrusion.
You may need to adjust your manual_z_home_pos setting in your firmware.
Printing in wood filament creates a nice feel to the thumb screw!
I used some of the design from WAIT24s KOSSEL ADJUSTER but ended up redesigning the whole thing so that it works better: http://www.thingiverse.com/thing:1407446
I used the nut hole from joecarpitas Spring Bed Leveling System (Kossel Clear, OpenBeam Printers) http://www.thingiverse.com/thing:1056185 I decided after using his thumb screw, that it was too sharp and I re-designed it with rounded nubs.
Let me know if you like it. I have a few other designs that I am working on for adjustable bed mounts that I will release after testing.