Good suggestion - but unless the background wall was similarly 'skewed' the shadow of the bolt would not appear to be parallel to the bolt itself from the left side through to the right.

I don't think the illusion is based on perspective because you can actually have it in hand and not be able to take the nail out.
For "Solitary Confinement", very same looking as our impossible object
Too bad the solution is missing (great site, thanks stanalger !). But maybe as a puzzle, the construction is completely different with a certain gimmick in wood. Like the first puzzle (golf in cage) there is a similar impossible object iron ball in cage but it cannot be free of cage.

the Sponge, sorry I misunderstand you and I am confused When you say "Yes, both of them", you mean you can do both "tooth and nail puzzle" or you mean "steaming and boiling" is needed? (or both

I have another theory for the second tooth and nail (http://www.johnrausch.com/PuzzleWorld/puz/img/tooth_and_nail_1.jpg ); The key words are expand and shrink wood...(that won't work for first one)
Nicolas