English verb conjugation
MUST FASTEN

Regular verb: fasten - fastened - fastened

Affirmation

Simple form	V-ing form
I must fasten you must fasten he must fasten we must fasten you must fasten they must fasten	I must be fastening you must be fastening he must be fastening we must be fastening you must be fastening they must be fastening
Perfect	V-ing perfect
I must have fastened you must have fastened he must have fastened we must have fastened you must have fastened they must have fastened	I must have been fastening you must have been fastening he must have been fastening we must have been fastening you must have been fastening they must have been fastening

Negation

Simple form	V-ing form
I mustn't fasten you mustn't fasten he mustn't fasten we mustn't fasten you mustn't fasten they mustn't fasten	I mustn't be fastening you mustn't be fastening he mustn't be fastening we mustn't be fastening you mustn't be fastening they mustn't be fastening
Perfect	V-ing perfect
I mustn't have fastened you mustn't have fastened he mustn't have fastened we mustn't have fastened you mustn't have fastened they mustn't have fastened	I mustn't have been fastening you mustn't have been fastening he mustn't have been fastening we mustn't have been fastening you mustn't have been fastening they mustn't have been fastening

Interrogative form

Simple form	V-ing form
must I fasten? must you fasten? must he fasten? must we fasten? must you fasten? must they fasten?	must I be fastening? must you be fastening? must he be fastening? must we be fastening? must you be fastening? must they be fastening?
Perfect	V-ing perfect
must I have fastened? must you have fastened? must he have fastened? must we have fastened? must you have fastened? must they have fastened?	must I have been fastening? must you have been fastening? must he have been fastening? must we have been fastening? must you have been fastening? must they have been fastening?

Interro-negative form

Simple form	V-ing form
mustn't I fasten? mustn't you fasten? mustn't he fasten? mustn't we fasten? mustn't you fasten? mustn't they fasten?	mustn't I be fastening? mustn't you be fastening? mustn't he be fastening? mustn't we be fastening? mustn't you be fastening? mustn't they be fastening?
Perfect	V-ing perfect
mustn't I have fastened? mustn't you have fastened? mustn't he have fastened? mustn't we have fastened? mustn't you have fastened? mustn't they have fastened?	mustn't I have been fastening? mustn't you have been fastening? mustn't he have been fastening? mustn't we have been fastening? mustn't you have been fastening? mustn't they have been fastening?