> Now I can not fix this, and even got one of those red squares trying!

It can be hard to fix things up later, it is definitely best to get things snapped together more accurately from the beginning.

Here's the kind of thing I mean - in the BRsSHat11.3dm that you posted earlier, here is a view from the right-hand side:



There is a natural baseline to this object, which I show there with the red line. Now if I zoom in to where that arrow is pointing (the left side edge of your baseline), it doesn't take very much zooming to see this:



The problem here is your baseline is just kind of floating at some arbitrary location, it's not aligned with the grid.

It would have probably been a lot easier to keep the accuracy high if you positioned the model so that this base line was running along the world axis line, like this:



You've got it set up nicely aligned with the other 2 world axis lines, like it is nicely positioned in the top view for the x and y axis lines. But you don't have it lined up nicely in elevation, and that's where you've got the accuracy problems in this case. (several pieces are on different z elevations)


If you do want to have your model at a more arbitrary elevation instead of z=0, then you should probably try to draw a reference line in there early on that spans across the whole width of your model, so it can be used as a common snapping target.

- Michael