The ridge is the top of the roof and the style of thatching varies, depending on material, local tradition or customer choice. listed thatch buildings require listed building consent to change from one ridge type to another.
A flush ridge may also be called a turnover, wrapover or buttup ridge. These ridges as described are flush with the main coatwork and are decorated with a spar and ligger pattern.
A block ridge is aptly named as it is a block of thatch on top of the roof, usually about 4 inches thick. This may be straight cut or patterned (Ornamental).
click the pictures below for more detail
Whilst most thatched roof coat work is Straw or Waterreed the ridges are primarily completed in straw.