Agree the line before the work begins
The useful starting point is the hedge you have now: its type, condition, approximate height and the room available to work. Not every hedge responds to a hard cut in the same way. The amount of green growth left and the season can affect the approach.
We look at the proposed height and width together. Bringing in the sides may free a route without reducing the screening you value. Where the top is uneven, we discuss a sensible line in relation to the existing plants rather than assuming every section can be made identical.
Please mention anything hidden in the hedge, such as wire, lights or supports. If it grows against a fence, show that side too. A clear view helps distinguish trimming the plants from a separate problem with the boundary.

