The last thing I shipped I actually bolted in place. It was an aluminum lower intake for a smallblock Ford. I bolted it to a piece of wood that was wider and longer than the intake and put it in a box that fit the wood fairly snug. I cut the box height down and used the doubled flaps on top, and I made up the air space with heavy paper, mostly to keep the cardboard from being able to crush over the voids. It made it to Missouri and back without damage. Stuff like that is not exactly fragile though, its literally just a hunk of metal with some holes in it. My bigger concern was it being dropped on the edge and smashing a gasket surface beyond repair.