This is another m3-nut thumb-wheel that goes on those extra long m3-screws to fix the bed for levelling. this here has a little "dome", which makes it easier to rotate if several are used stacked upon each other, also you can easy see on which side the nut is! Standard M3-nut fits nicely inside and is flush with the surface. 2 should be used per each of the 3 fixing points: 1 above and 1 below the bottom-plate OPPOSING each other (like on the photo) to clamp everything in place - this forms a "sandwich" with a stable plate in the middle, the abs and finally the metal nut. 2 springs in the front make levelling easier (third in the middle back is fixed/does not need a spring). That means there have to be printed out 6 in total, for 3-point bed-leveling (as seen in photo). Partly inspired by http://www.thingiverse.com/thing:13778 and http://www.thingiverse.com/thing:346812Recommended: Print in ABS, solid or dense infill, 0.1 resolution