It's this fourth dimension that makes things tricky. Were it not for this dimension, anyone with good measuring tools and the ability to read them could ascertain balance. Somewhere along the line, long before the hoof protractor was invented, some fellow who probably had never shod horses decided that 45 degrees was the proper toe angle for front hooves. This erroneous idea has been passed down in books from around 1800 to the present. Such a low angle is out of balance for most horses.
Many farriers consider the shoulder angle when determining the toe angle for the fore hooves.
This can be indeed be useful. Although the hoof need not necessarily be at the same angle as the shoulder, a relatively steep or low shoulder angle may indicate a correspondingly steep or low hoof angle. The methods of establishing the correct toe angle usually apply to the fore hooves. The hinds are commonly the same as the fores, or slightly more upright. But we have yet to factor in time .