The term 'well-built' is used to describe something that is strong and durable. This can be seen in the three crossword solutions: SOLID (5 letters), STURDY (6 letters), and ROBUST (6 letters). SOLID implies that the object is firm and not easily broken, while STURDY suggests that it is strong and resistant to wear and tear. Finally, ROBUST implies that the object is strong and able to withstand harsh conditions. All three words together paint a picture of something that is well-built and able to stand the test of time.