I could nail you could nail he could nail we could nail you could nail they could nail
V-ing form
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
I could have nailed you could have nailed he could have nailed we could have nailed you could have nailed they could have nailed
V-ing perfect
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
I could not nail you could not nail he could not nail we could not nail you could not nail they could not nail
V-ing form
I could not be nailing you could not be nailing he could not be nailing we could not be nailing you could not be nailing they could not be nailing
Perfect
I could not have nailed you could not have nailed he could not have nailed we could not have nailed you could not have nailed they could not have nailed
V-ing perfect
I could not have been nailing you could not have been nailing he could not have been nailing we could not have been nailing you could not have been nailing they could not have been nailing
Interrogative form
Simple form
could I nail? could you nail? could he nail? could we nail? could you nail? could they nail?
V-ing form
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
could I have nailed? could you have nailed? could he have nailed? could we have nailed? could you have nailed? could they have nailed?
V-ing perfect
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
could I not nail? could you not nail? could he not nail? could we not nail? could you not nail? could they not nail?
V-ing form
could I not be nailing? could you not be nailing? could he not be nailing? could we not be nailing? could you not be nailing? could they not be nailing?
Perfect
could I not have nailed? could you not have nailed? could he not have nailed? could we not have nailed? could you not have nailed? could they not have nailed?
V-ing perfect
could I not have been nailing? could you not have been nailing? could he not have been nailing? could we not have been nailing? could you not have been nailing? could they not have been nailing?