No. Eastern Orthodox use this devotion as well, with the exception that after touching the forehead and chest they touch right shoulder to left shoulder. Most Catholics touch left shoulder to right shoulder. Some high-church Protestants may also use this devotion in their prayer.
Dave Kacz:
And is it a requirement to begin and end every prayer?
No. The sign of the cross is a private devotion and thus it is not incumbant upon any Catholic to practice it. It is, however, an ancient prayer custom and well worth considering. For more information, I recommend the following book:
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