Installation of the Y-axis rails may be easier if you place the V-Core 3 frame upside down

350mm MGN12 Linear Rail Assembly

Insert the linear rail into the 3030 extrusion

Position the linear rail so that its end touches the 3030 cast corner bracket as shown

Install the two MGN12 3030 alignment tools as shown, this will make sure the linear rail is positioned correctly

Fasten the marked M3x12 screws, starting from one end

Remove the MGN12 3030 alignment tools and repeat these steps for the linear rail on the opposite side