must thumbtack
Regular verb: thumbtack - thumbtacked- thumbtacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must thumbtack
you must thumbtack
she must thumbtack
we must thumbtack
you must thumbtack
they must thumbtack 	I must be thumbtacking
you must be thumbtacking
she must be thumbtacking
we must be thumbtacking
you must be thumbtacking
they must be thumbtacking	I must have thumbtacked
you must have thumbtacked
she must have thumbtacked
we must have thumbtacked
you must have thumbtacked
they must have thumbtacked	I must have been thumbtacking
you must have been thumbtacking
she must have been thumbtacking
we must have been thumbtacking
you must have been thumbtacking
they must have been thumbtacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't thumbtack
you mustn't thumbtack
she mustn't thumbtack
we mustn't thumbtack
you mustn't thumbtack
they mustn't thumbtack 	I mustn't be thumbtacking
you mustn't be thumbtacking
she mustn't be thumbtacking
we mustn't be thumbtacking
you mustn't be thumbtacking
they mustn't be thumbtacking	I mustn't have thumbtacked
you mustn't have thumbtacked
she mustn't have thumbtacked
we mustn't have thumbtacked
you mustn't have thumbtacked
they mustn't have thumbtacked	I mustn't have been thumbtacking
you mustn't have been thumbtacking
she mustn't have been thumbtacking
we mustn't have been thumbtacking
you mustn't have been thumbtacking
they mustn't have been thumbtacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I thumbtack?
must you thumbtack?
must she thumbtack?
must we thumbtack?
must you thumbtack?
must they thumbtack? 	must I be thumbtacking?
must you be thumbtacking?
must she be thumbtacking?
must we be thumbtacking?
must you be thumbtacking?
must they be thumbtacking? 	must I have thumbtacked?
must you have thumbtacked?
must she have thumbtacked?
must we have thumbtacked?
must you have thumbtacked?
must they have thumbtacked? 	must I have been thumbtacking?
must you have been thumbtacking?
must she have been thumbtacking?
must we have been thumbtacking?
must you have been thumbtacking?
must they have been thumbtacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I thumbtack?
mustn't you thumbtack?
mustn't she thumbtack?
mustn't we thumbtack?
mustn't you thumbtack?
mustn't they thumbtack? 	mustn't I be thumbtacking?
mustn't you be thumbtacking?
mustn't she be thumbtacking?
mustn't we be thumbtacking?
mustn't you be thumbtacking?
mustn't they be thumbtacking? 	mustn't I have thumbtacked?
mustn't you have thumbtacked?
mustn't she have thumbtacked?
mustn't we have thumbtacked?
mustn't you have thumbtacked?
mustn't they have thumbtacked? 	mustn't I have been thumbtacking?
mustn't you have been thumbtacking?
mustn't she have been thumbtacking?
mustn't we have been thumbtacking?
mustn't you have been thumbtacking?
mustn't they have been thumbtacking?