Some years ago I bought a gardenbook which won't gather dust at my bookshelves as it is practical and very didactically illustrated.
References: "Pruning and Training Plants. A complete guide." written by David Joyce and published by Mitchell Beazley, London, 2002.
After several years of rather prudent and thus superficial pruning my hedges of Carpinus betulus became too thick with a lot of leaves at the end of the twigs and none or only a few in the interior of the plants.
When there is no immediate frost in sight we can renovate such a hedge by severe pruning. In the first year we begin with pruning only one side of the hedge. After having shorten the top back to the required height we cut all the branches on onse side back to the main stem(s).
Once this side has made good growth we'll tackle the other face as severely as the first.
