Here is a close up of the connectors with the hole drilled in them. You can see how the bolt fits through. It is very sturdy and works great. There is a nut above and below the connector to stop it from sliding through.
Sorry, I should have posted the link for this so people would realize they were meant to go together. If you look at the picture of the whole cage, it's a large cage underneath for 3 of my boars, and the upper level is a separate 2x4 cage for my older boar. I have just had my one female spayed due to an ovarian cyst and will be introducing her into the 2x4 soon.
You could use this idea for a second level as well. You would need to create a longer ramp though so the ramp wouldn't be too steep.
If you don't put a nut on the very top above the upper connector, you can lift the whole top cage off for cleaning if you want as well! With my set up I find it just as easy to pull the whole cage out from the wall and go in behind it and change it where it is - but some might find it useful to be able to remove the top cage.
So, you drill a hole the whole way through - I take it no probs with the plastic breaking - then put a long bolt right through, and secure with uts at either end?
Exactly. The hole is drilled all the way through, right in the middle. We had no problems at all with the plastic breaking - it's very sturdy stuff. Then the nuts just make it so the bolt can't slide. You can see how easy it would be to adjust the height if you wanted to. Just give the nuts a few turns one way or the other. We made the bolts longer than we ever expected to need, just in case. The excess just slides down beside the grids and is not accessible to the piggies at all. If you look closely in the picture, you can see the bolt extends quite a few inches below the connector. The bolt came in a 6' piece, and we cut it into 12" pieces.
The pro here who did the drilling says he used a drill bit that was a bit smaller than the bolt to avoid drilling off-centre. Then he took a 1/4 inch round file, put it in the drill, and ran it through there to make it the right size. That way the hole is a little bit bigger than the bolt (but not much).
