A flysheet is waterproof on the outside and also provides a surface to collect condensation on the inside, which then runs down to the ground.
A flysheet was sometimes recommended and the poles could be made of bamboo.
When a flysheet is used, it is important that there be no contact with the inner tent it is protecting; this keeps the inner dry.
These may be single wall, or single-wall with partial flysheet, or double wall.
