alternative incline crunch..`?

OK, here's the deal..
I don't have any access to a gym, so I'm working out at home, which is fine. I just have a little problem: I don't have a bench that can be adjusted to go incline or decline or whatever. Therefor, do any of you guys know a way to make the incline crunch without using a bench? I'm talking about using chairs, tables or something like that?

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bump.

What about a stability ball? Not very expensive. It allows you to get a good pre-stretch in your abdominals before performing the concentric contraction. The ROM is actually greater than the board or the floor.

Maybe rig something up on the stairs?