Why is it better to have round manhole covers than square ones?
This is logical rather than lateral, but it is a good puzzle which can be solved by lateral thinking techniques. It is supposedly used by a very well-known software company as an interview question for prospective employees. Solution A square manhole cover can be turned and dropped down the diagonal of the manhole. A round manhole cannot be dropped down the manhole. So for safety and practicality, all manhole covers should be round.
Another answer especially valuable for heavy covers: it fits in any position and does not need adjustment while the square might need adjustment for up to 45 degees in one or the other direction...