I must lock you must lock he must lock we must lock you must lock they must lock
V-ing form
I must be locking you must be locking he must be locking we must be locking you must be locking they must be locking
Perfect
I must have locked you must have locked he must have locked we must have locked you must have locked they must have locked
V-ing perfect
I must have been locking you must have been locking he must have been locking we must have been locking you must have been locking they must have been locking
Negation
Simple form
I mustn't lock you mustn't lock he mustn't lock we mustn't lock you mustn't lock they mustn't lock
V-ing form
I mustn't be locking you mustn't be locking he mustn't be locking we mustn't be locking you mustn't be locking they mustn't be locking
Perfect
I mustn't have locked you mustn't have locked he mustn't have locked we mustn't have locked you mustn't have locked they mustn't have locked
V-ing perfect
I mustn't have been locking you mustn't have been locking he mustn't have been locking we mustn't have been locking you mustn't have been locking they mustn't have been locking
Interrogative form
Simple form
must I lock? must you lock? must he lock? must we lock? must you lock? must they lock?
V-ing form
must I be locking? must you be locking? must he be locking? must we be locking? must you be locking? must they be locking?
Perfect
must I have locked? must you have locked? must he have locked? must we have locked? must you have locked? must they have locked?
V-ing perfect
must I have been locking? must you have been locking? must he have been locking? must we have been locking? must you have been locking? must they have been locking?
Interro-negative form
Simple form
mustn't I lock? mustn't you lock? mustn't he lock? mustn't we lock? mustn't you lock? mustn't they lock?
V-ing form
mustn't I be locking? mustn't you be locking? mustn't he be locking? mustn't we be locking? mustn't you be locking? mustn't they be locking?
Perfect
mustn't I have locked? mustn't you have locked? mustn't he have locked? mustn't we have locked? mustn't you have locked? mustn't they have locked?
V-ing perfect
mustn't I have been locking? mustn't you have been locking? mustn't he have been locking? mustn't we have been locking? mustn't you have been locking? mustn't they have been locking?