Here's how Howling Wolf did it on his famous 'rocking chair' album. I got these as Harry' blues lyrics site.

BACK DOOR MAN
(Willie Dixon)

I am, a back door man
I am, a back door man
Well the, men don't know, but the little girls understand

When everybody's tryin' to sleep
I'm somewhere making my, midnight creep
Yes in the morning, when the rooster crow Something tell me, I got to go

I am, a back door man
I am, a back door man

Well the, men don't know, but little girls understand
They, take me to the doctor, shot full o' holes
Nurse cried, please save the soul
Killed him for murder, first degree
Judge's wife cried, let the man go free

I am, a back door man
I am, a back door man
Well the, men don't know, but little girls understand

Stand out there, cop's wife cried
Don't take him down, rather be dead
Six feets in the ground
When you come home you can eat, pork and beans
I eats mo' chicken, any man seen

I am, a back door man
I am, a back door man

--Stewie.