must sheathe
Regular verb: sheathe - sheathed- sheathed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must sheathe
you must sheathe
he must sheathe
we must sheathe
you must sheathe
they must sheathe 	I must be sheathing
you must be sheathing
he must be sheathing
we must be sheathing
you must be sheathing
they must be sheathing	I must have sheathed
you must have sheathed
he must have sheathed
we must have sheathed
you must have sheathed
they must have sheathed	I must have been sheathing
you must have been sheathing
he must have been sheathing
we must have been sheathing
you must have been sheathing
they must have been sheathing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't sheathe
you mustn't sheathe
he mustn't sheathe
we mustn't sheathe
you mustn't sheathe
they mustn't sheathe 	I mustn't be sheathing
you mustn't be sheathing
he mustn't be sheathing
we mustn't be sheathing
you mustn't be sheathing
they mustn't be sheathing	I mustn't have sheathed
you mustn't have sheathed
he mustn't have sheathed
we mustn't have sheathed
you mustn't have sheathed
they mustn't have sheathed	I mustn't have been sheathing
you mustn't have been sheathing
he mustn't have been sheathing
we mustn't have been sheathing
you mustn't have been sheathing
they mustn't have been sheathing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I sheathe?
must you sheathe?
must he sheathe?
must we sheathe?
must you sheathe?
must they sheathe? 	must I be sheathing?
must you be sheathing?
must he be sheathing?
must we be sheathing?
must you be sheathing?
must they be sheathing? 	must I have sheathed?
must you have sheathed?
must he have sheathed?
must we have sheathed?
must you have sheathed?
must they have sheathed? 	must I have been sheathing?
must you have been sheathing?
must he have been sheathing?
must we have been sheathing?
must you have been sheathing?
must they have been sheathing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I sheathe?
mustn't you sheathe?
mustn't he sheathe?
mustn't we sheathe?
mustn't you sheathe?
mustn't they sheathe? 	mustn't I be sheathing?
mustn't you be sheathing?
mustn't he be sheathing?
mustn't we be sheathing?
mustn't you be sheathing?
mustn't they be sheathing? 	mustn't I have sheathed?
mustn't you have sheathed?
mustn't he have sheathed?
mustn't we have sheathed?
mustn't you have sheathed?
mustn't they have sheathed? 	mustn't I have been sheathing?
mustn't you have been sheathing?
mustn't he have been sheathing?
mustn't we have been sheathing?
mustn't you have been sheathing?
mustn't they have been sheathing?