To know a hawk from a hernshaw is an ancient proverb, sometimes corrupted into handsaw.
"Hamlet"
William Shakespeare
I know a hawk from a handsaw, or my name's not William Shakespeare."
"A Cotswold Village"
J. Arthur Gibbs
The sole of the plane is formed of a plate of tempered steel about the thickness of a handsaw, according to the length required, and this plate is adapted to the curve, and is securely fixed at each end.
"Woodworking Tools 1600-1900"
Peter C. Welsh