Hi David - first off: the title is a bit misleading as there are no mesh objects in this file. We call this type of object a polysurface.
Secondly, the holes at the ends are not really a problem. The edges at those locations are planar and simply capping the object would close these holes.
The problem is that two pairs of surfaces on one side of the object are overlapping each other and you will have to fix that first.
In the attached, I have just deleted a few surfaces (placed on a separate layer so that you can see which ones) and then mirrored good surfaces from the other side of the object. After that, a few extra surfaces in between are created with the
EdgeSrf command. Joining all of these creates a closed object.
TheresAHoleInIt-wd.3dm (2.3 MB)
Note that there are a few very narrow slices of surfaces that I overlooked at first. You’re getting very close to the document tolerances on these and you should generally avoid creating these.