i posted this over on the makergear group so i wanted to add it here as well. this was designed for the makergear m2. i know we have people here with other types of printers and it may work for them as well. it measures 150mm x 200mm. hopefully it will help some people out.
so it seems alot of people have trouble getting their z-height adjusted properly and bed leveled, myself included so i made a gcode calibration file to assist with this. this is sized specifically for the m2 bed size. i attached a pic of the file so you can see what i have goin on. this will print a single layer of what you see in the pic, 2 lines wide. the outer 3 boxes are for you to fine tune your bed level. this whole thing prints real slow so you can make small tweaks while its printing. if you lines are squished on one corner but high and round on another then you can visibly see that and adjust accordingly. the boxes, 0.0 and the center line all print at your currently set z-height. the other stripes are printed at their labeled height. your m4 z-height adjustment screw should have a thread pitch of .7mm so basically if you turn your screw in either direction 1/2 a flat on the head you will adjust the bed roughly .05mm. just run the gcode, see what you got and which way you need to move and by how much. keep in mind this is to FINE tune the machine. you'll need to get it close before hand. another note is i have the layers set at .15 and temps are set more for abs. enjoy!!!