| # | Clue | Answer As Given | Value | Round | Category | Air Date | Show |
|---|---|---|---|---|---|---|---|
| Created to span more distance than a horizontal bridge, it's supported by diagonal surfaces called skewbacks | arch | $2,000 | DJ | ENGINEERING | 2003-06-23 | #4346 | |
| Though Romans used this support principle for aqueducts, it wasn't applied to dams until the 6th C. | the arch | $1,000 | DJ | ENGINEERING | 1988-02-04 | #794 |