In W. B. Yeats' poem 'Father and Daughter' the speaker is apparently the father of a young daughter who is in relations with a boy or man without her father's blessing. The father is the kind of man who is generous with his love, especially with his daughter. He is also the kind of father who wants the best for his little girl, not being afraid of firm disciplinary actions to help his daughter grow in the right direction. The problem the father has with his daughter is her relations with someone who he does not see well enough for her. He wants her to have someone who is more of what he wants for her. The father is banning her from being close to him. He is keeping her at a distance as she is unintentionally hurting him with the decisions she is making. The father is speaking to someone whom he respects, looking for advice to mold her into what he wants her to be.
Yeats' point in his poem is people who are experienced with age, look for different qualities in a person than someone who is young and inexperienced.
'She hears me strike the board and say' in the first line lets the reader know the speaker has some built up frustration with the individual mentioned. The father is putting his foot down about the subject. He is just fed up with his daughter's actions and is laying down the law.
'That she is under ban', is the resolve the father has with his daughter until her relationship with the man changes to the father's liking or ceases altogether. This is the father's way of shielding himself from his daughter's actions. He cannot have her close to his heart or she will hurt him...