English verb conjugation
COULD NAIL

Regular verb: nail - nailed - nailed

Affirmation

Simple form	V-ing form
I could nail you could nail he could nail we could nail you could nail they could nail	I could be nailing you could be nailing he could be nailing we could be nailing you could be nailing they could be nailing
Perfect	V-ing perfect
I could have nailed you could have nailed he could have nailed we could have nailed you could have nailed they could have nailed	I could have been nailing you could have been nailing he could have been nailing we could have been nailing you could have been nailing they could have been nailing

Negation

Simple form	V-ing form
I couldn't nail you couldn't nail he couldn't nail we couldn't nail you couldn't nail they couldn't nail	I couldn't be nailing you couldn't be nailing he couldn't be nailing we couldn't be nailing you couldn't be nailing they couldn't be nailing
Perfect	V-ing perfect
I couldn't have nailed you couldn't have nailed he couldn't have nailed we couldn't have nailed you couldn't have nailed they couldn't have nailed	I couldn't have been nailing you couldn't have been nailing he couldn't have been nailing we couldn't have been nailing you couldn't have been nailing they couldn't have been nailing

Interrogative form

Simple form	V-ing form
could I nail? could you nail? could he nail? could we nail? could you nail? could they nail?	could I be nailing? could you be nailing? could he be nailing? could we be nailing? could you be nailing? could they be nailing?
Perfect	V-ing perfect
could I have nailed? could you have nailed? could he have nailed? could we have nailed? could you have nailed? could they have nailed?	could I have been nailing? could you have been nailing? could he have been nailing? could we have been nailing? could you have been nailing? could they have been nailing?

Interro-negative form

Simple form	V-ing form
couldn't I nail? couldn't you nail? couldn't he nail? couldn't we nail? couldn't you nail? couldn't they nail?	couldn't I be nailing? couldn't you be nailing? couldn't he be nailing? couldn't we be nailing? couldn't you be nailing? couldn't they be nailing?
Perfect	V-ing perfect
couldn't I have nailed? couldn't you have nailed? couldn't he have nailed? couldn't we have nailed? couldn't you have nailed? couldn't they have nailed?	couldn't I have been nailing? couldn't you have been nailing? couldn't he have been nailing? couldn't we have been nailing? couldn't you have been nailing? couldn't they have been nailing?