Beggars' Choice

A friend of mine is considering adding an extra storey on his house. After cogitating for several minutes we decided that the cheapest and most efficient way to do this would be to drop a shipping crate on the roof. The rationale is that it would crush the roof, thereby abutting the existing structure quite nicely. The problem of water runoff from the flat roof of the crate had us stumped for a while, until we realised that the chances of it landing perfectly level would be about nil.

Brilliant! You know it makes sense.