should knuckle
Regular verb: knuckle - knuckled- knuckled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I should knuckle
you should knuckle
he should knuckle
we should knuckle
you should knuckle
they should knuckle 	I should be knuckling
you should be knuckling
he should be knuckling
we should be knuckling
you should be knuckling
they should be knuckling	I should have knuckled
you should have knuckled
he should have knuckled
we should have knuckled
you should have knuckled
they should have knuckled	I should have been knuckling
you should have been knuckling
he should have been knuckling
we should have been knuckling
you should have been knuckling
they should have been knuckling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I should not knuckle
you should not knuckle
he should not knuckle
we should not knuckle
you should not knuckle
they should not knuckle 	I should not be knuckling
you should not be knuckling
he should not be knuckling
we should not be knuckling
you should not be knuckling
they should not be knuckling	I should not have knuckled
you should not have knuckled
he should not have knuckled
we should not have knuckled
you should not have knuckled
they should not have knuckled	I should not have been knuckling
you should not have been knuckling
he should not have been knuckling
we should not have been knuckling
you should not have been knuckling
they should not have been knuckling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
should I knuckle?
should you knuckle?
should he knuckle?
should we knuckle?
should you knuckle?
should they knuckle? 	should I be knuckling?
should you be knuckling?
should he be knuckling?
should we be knuckling?
should you be knuckling?
should they be knuckling? 	should I have knuckled?
should you have knuckled?
should he have knuckled?
should we have knuckled?
should you have knuckled?
should they have knuckled? 	should I have been knuckling?
should you have been knuckling?
should he have been knuckling?
should we have been knuckling?
should you have been knuckling?
should they have been knuckling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
should I not knuckle?
should you not knuckle?
should he not knuckle?
should we not knuckle?
should you not knuckle?
should they not knuckle? 	should I not be knuckling?
should you not be knuckling?
should he not be knuckling?
should we not be knuckling?
should you not be knuckling?
should they not be knuckling? 	should I not have knuckled?
should you not have knuckled?
should he not have knuckled?
should we not have knuckled?
should you not have knuckled?
should they not have knuckled? 	should I not have been knuckling?
should you not have been knuckling?
should he not have been knuckling?
should we not have been knuckling?
should you not have been knuckling?
should they not have been knuckling?