A saddle is the join where one roof cuts into a main roof of a thatched building. It is a section at a junction between the main roof coatwork and a lower section.
A thatched saddle is sometimes protected with lead, although it is not a necessity. This may be due to personal preference or because the roof design means that it will be taking a lot of water and so this may reduce additional wear.
Saddles may vary depending on the roof design, here are a few examples.