Gutter

A channel to collect water and snow melt at the eaves of a roof.

Constructed of steel, copper, aluminum, or plastic compounded with other materials to increase strength and wearing and rust resistance, positioned just below and along the eaves of a building.

The fall on guttering does vary, but a good guide is 1 in 600 which is 5mm fall over a 3m length. Perhaps obvious but the lowest point is where the downpipe fits.