English verb conjugation
COULD LOCK

Regular verb: lock - locked - locked

Affirmation

Simple form	V-ing form
I could lock you could lock he could lock we could lock you could lock they could lock	I could be locking you could be locking he could be locking we could be locking you could be locking they could be locking
Perfect	V-ing perfect
I could have locked you could have locked he could have locked we could have locked you could have locked they could have locked	I could have been locking you could have been locking he could have been locking we could have been locking you could have been locking they could have been locking

Negation

Simple form	V-ing form
I couldn't lock you couldn't lock he couldn't lock we couldn't lock you couldn't lock they couldn't lock	I couldn't be locking you couldn't be locking he couldn't be locking we couldn't be locking you couldn't be locking they couldn't be locking
Perfect	V-ing perfect
I couldn't have locked you couldn't have locked he couldn't have locked we couldn't have locked you couldn't have locked they couldn't have locked	I couldn't have been locking you couldn't have been locking he couldn't have been locking we couldn't have been locking you couldn't have been locking they couldn't have been locking

Interrogative form

Simple form	V-ing form
could I lock? could you lock? could he lock? could we lock? could you lock? could they lock?	could I be locking? could you be locking? could he be locking? could we be locking? could you be locking? could they be locking?
Perfect	V-ing perfect
could I have locked? could you have locked? could he have locked? could we have locked? could you have locked? could they have locked?	could I have been locking? could you have been locking? could he have been locking? could we have been locking? could you have been locking? could they have been locking?

Interro-negative form

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