Wed February 20, 2013 By:

a 2D cut out which when folded gives a solid shape

Expert Reply
Thu February 21, 2013
A very simple example of this can be a rectangular 2D piece cut out, which can be folded to give a both sides open cylinder or it can be cut in the shape of a plus (+) sign, with one long arm and that can be folded over to give a cube/cuboid. Similarly, you can make prisms, cone using 2D paper cut outs. 
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