Item dupe glitch?

Is there any known item dupe glitch for SMP?

I want some TNT.

Im not sure if this is still working but;

-


Open up inventory, close inentory

Go to inventory chest, put in desired item.

Close inventory chest

Close and press save and quit

Return

Open chest

Put desired item into inventory

Close out minecraft via red x on top right

Duped.

Nope. They have all been patched. Just build a big underground trap and farm some gunpowder. Or whatever the hell the decided to rename it as.