(Manual) Calibration points for my Prusa I3:

G1 F3000
G1 X0 Y30
G1 X0 Y200
G1 X150 Y200
G1 X150 Y30

More objects to make:

Some notes on auto bed levelling:

Just a few things left to do:

[x] Cut 5/16 smooth rod to fit Z and X axes.
[x] Cut M5 threaded rod to fit Z axes.
[ ] Turn hobbed bolt to actually fit through 608 bearing.
[x] CAD up print surface.
[ ] Laser up print surface.
[ ] Mount and wire up limit switches.

Which means a little shopping left.

[ ] 4x M3 hex screw for print surface levelling.  Length 20mm?
[ ] 1x M5 hex screw to draw m5 nuts into place.
[x] 6mm acrylic for print surface. (Found in the shop).
[ ] Blue painters tape.
[ ] 5mm ID aquarium tubing.
[ ] 4x 8mm? ID hose clamps.