thumb|300px|right In the 2008 movie, Iron Man, Jeff Bridges' character, Obadiah Stane, has ordered the scientists at Stark Industries to build an arc reactor. When one of the scientists tells him that it can't be done, Stane exclaims, "Tony Stark was able to build this in a cave! With a box of scraps!"
To build something in a cave with a box of scraps means to build something that shouldn't be able to work given the limitations of normal people.
Examples of things built in a cave, with a box of scraps
jmdbcool was able to build working DDR pads with wood and sheet metal.
Forge's super power is basically building things in a cave with a box of scraps.