must lock
Regular verb: lock - locked- locked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must lock
you must lock
he must lock
we must lock
you must lock
they must lock 	I must be locking
you must be locking
he must be locking
we must be locking
you must be locking
they must be locking	I must have locked
you must have locked
he must have locked
we must have locked
you must have locked
they must have locked	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 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't lock
you mustn't lock
he mustn't lock
we mustn't lock
you mustn't lock
they mustn't lock 	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	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	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 	V-ing form 	Perfect 	V-ing perfect 	
must I lock?
must you lock?
must he lock?
must we lock?
must you lock?
must they lock? 	must I be locking?
must you be locking?
must he be locking?
must we be locking?
must you be locking?
must they be locking? 	must I have locked?
must you have locked?
must he have locked?
must we have locked?
must you have locked?
must they have locked? 	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 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I lock?
mustn't you lock?
mustn't he lock?
mustn't we lock?
mustn't you lock?
mustn't they lock? 	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? 	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? 	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?