This is an adjustable Y endstop holder for a Prusa i3 with alluminum carriage

It has a clamp that keep in position the endstop holder using the two M8 rods

The adjustable plate is fixed to the metal carriage

Parts 3-4-6-7 have nuts co-molded, so you have to pause the printing and insert the nut

have a look at my previous thing where I explain better how to insert a nut inside the printing (http://www.thingiverse.com/thing:587659/#instructions)