A word is in order concerning trees that are used in hedges or as windbreak trees. No, not all hedge plants are shrubs, such as those discussed on Page 1.
Arborvitae trees have a dense growth habit that makes them popular privacy screens or windbreak trees (arborvitaes are also found in shrub-form, if you're seeking a shorter hedge). In Europe, European Beech Trees have been used for centuries as privacy screens and windbreak trees. As noted on Page 1, windbreak trees are commonly allowed to grow naturally, rather than trimmed to a particular size and shape, unless you wish to combine decorative and practical functions.
Canadian hemlocks (Tsuga canadensis) are among the easiest trees to prune into hedges. MacPhailWoods.org states, "Prune hemlock lightly but often during the first few growing seasons (two to three times from late June to late August for two to three years). After three years prune once, in late June, as with white spruce." The site cautions against cutting the leaders until the hemlock hedge or windbreak has attained the height you envisioned for it.
There is even a tree known as the "hedge maple." I introduce you to it at the end of my article on the different types of maples.