An adapter / holder to mount an SK8 linear rail shaft at the right height on an Anet AM8 / PK8 / PK6 2040 aluminum profile. The linear rail is about 3mm above the upper side of the 2040 extrusion or about 7mm for the center of the rail.
SK8 linear rail shaft used
The 2040 profile is Nut 5 and all bolts and nuts are M5.
FreeCad 0.18 file attached.
I printed it with 5 perimeters (0.4mm nozzle) to get the strongest part there where the bolts are tighten. 4 bottom and top layers.