Adjustable supports for the rain gutter are placed in approximate position.
Align the outside of the gutter with the slope of the roof using a board on the roof.
Establish level and mark the brace. Place a second mark to establish downward slope.
The slope was arbitrarily chosen to be about 1.25 cm in 3 Meters (1/2" : 10'). The top of the sliding brace is below the mark because lowering this end lifted the control board at the high end, like a teeter totter. Adjusting this support system is easy.