I want to put a cap on my chimney to keep the squirrels from dropping debris
into the flue. The chimney actually has 3 terracotta pipes at the top. They
are side-by-side and form a large rectangle

-------------------------
| 1 | 2 | 3 |
| | | |
-------------------------

Do I have to get a cap to cover all three? I look at other chimneys and it
seems many have a cap on just one of the pipes. What are the different
pipes?

Thanks,
Dave