First Print with the Simple - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 89

Note
I mentioned g-code earlier in the topic, but now you can see what it ac-
tually looks like. It's very cryptic stuff, but it's basically just code that
tells the various motors how to operate. X10, for example, tells the X
motor to spin in such a way that the print bed moves 10mm. The g-
code Z-15 would tell the Z motor to spin the lead screw so that the hot
end moves down (toward) to the print bed. You'll also see the various
settings you configured for Repetier back in Chapter 4 submitted via
g-code. If you'd like to see just how substantial the list of commands/
codes for g-code really is, visit http://en.wikipedia.org/wiki/G-code .
Home the Hot End
Look at your Simple (or whatever 3D printer you are currently using) and take
note of where the end of the hot end's nozzle is located. Figure 5.10 shows where
my Simple's nozzle is located. It's about 5cm above the print bed and slightly to
the left of dead center. It's also more toward the rear of the print bed.