Add nuts to your shapeOko table in order to allow you to easily block items.
Then use this clamp (http://www.thingiverse.com/thing:414437).
This will also avoid your table to deform as it's also a foot ;-)
I put a 5 pieces version, if you use the "Ditto Printing", this will really speed-up the production process...
Shapeoko_Nut_Foot_v1-5.stl | 438.0KB |