<p>The Funssor CNC XY joiner is hollow where the X limit switch should hit a stop. Unfortunately, I noticed this issue only after completing assembly and alignment of the RatRig V-Core4 X gantry, rails, toolheads, belts, and wiring up the X axis limit switch…so…..</p><p>If you notice this issue much earlier in the build than I did, you can use @Brigandier's stop. This mod of that stop allows the insert to clear the rail and be tilted into place, then slid into the Funssor CNC XY joiner. &nbsp;One advantage of this mod is that it can be removed and replaced later should you either damage it or want to change materials or colors.&nbsp;<br><br>The STL contains 2 identical parts, as 2 of them are needed.</p><p>Two versions are included:</p><ol><li>PPA-CF version - can be used for materials with little to no shrink. &nbsp;</li><li>ABS version - X, Y were increased by 2% to account for ABS shrink.&nbsp;</li></ol><p>After printing, you might find it desirable to further tweak the X, Y scale in the slicer to get a perfect fit for your material.</p><p>Photos 1-4 show how to tip the block in to place, and insert the retaining flathead screw.</p>