could knurl
Regular verb: knurl - knurled- knurled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could knurl
you could knurl
she could knurl
we could knurl
you could knurl
they could knurl 	I could be knurling
you could be knurling
she could be knurling
we could be knurling
you could be knurling
they could be knurling	I could have knurled
you could have knurled
she could have knurled
we could have knurled
you could have knurled
they could have knurled	I could have been knurling
you could have been knurling
she could have been knurling
we could have been knurling
you could have been knurling
they could have been knurling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't knurl
you couldn't knurl
she couldn't knurl
we couldn't knurl
you couldn't knurl
they couldn't knurl 	I couldn't be knurling
you couldn't be knurling
she couldn't be knurling
we couldn't be knurling
you couldn't be knurling
they couldn't be knurling	I couldn't have knurled
you couldn't have knurled
she couldn't have knurled
we couldn't have knurled
you couldn't have knurled
they couldn't have knurled	I couldn't have been knurling
you couldn't have been knurling
she couldn't have been knurling
we couldn't have been knurling
you couldn't have been knurling
they couldn't have been knurling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I knurl?
could you knurl?
could she knurl?
could we knurl?
could you knurl?
could they knurl? 	could I be knurling?
could you be knurling?
could she be knurling?
could we be knurling?
could you be knurling?
could they be knurling? 	could I have knurled?
could you have knurled?
could she have knurled?
could we have knurled?
could you have knurled?
could they have knurled? 	could I have been knurling?
could you have been knurling?
could she have been knurling?
could we have been knurling?
could you have been knurling?
could they have been knurling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I knurl?
couldn't you knurl?
couldn't she knurl?
couldn't we knurl?
couldn't you knurl?
couldn't they knurl? 	couldn't I be knurling?
couldn't you be knurling?
couldn't she be knurling?
couldn't we be knurling?
couldn't you be knurling?
couldn't they be knurling? 	couldn't I have knurled?
couldn't you have knurled?
couldn't she have knurled?
couldn't we have knurled?
couldn't you have knurled?
couldn't they have knurled? 	couldn't I have been knurling?
couldn't you have been knurling?
couldn't she have been knurling?
couldn't we have been knurling?
couldn't you have been knurling?
couldn't they have been knurling?