What is required of a letter of appointment for a volunteer work visa?

by Rachel

Question: What does the letter of appointment need to consist of in order to file for a visa to volunteer for about a year at an orphanage in N. Uganda?

Answer: The Rachel for this inquiry. I would think including the Name of the Orphanage, location contact person; time the the volunteer will spend; and reason for choosing the said orphanage should be enough for this kind of appointment letter.
Of course some details about the volunteer should be included in the letter.