If you're going to get a hole drilled into your skull, you don't want to use just any tool. (Though most of us would avoid the skull-drilling in the first place.) One researcher used four different instruments on a single skull to compare Neolithic trepanation methods.
Photo from Science Museum, London.
Dr. Thomas Wilson Parry (1866-1945) owned this particular skull, which he used to perform practical research on trepanation. He performed roughly 50 trepanation experiments on the skulls of the more and less recent deceased, using in this case a shark’s tooth, a flint-pointed bow drill, a flint scraper, and obsidian to achieve the variety of holes. Parry published Trephination of the Living Human Skull in Prehistoric Times in 1923, but far more amusing is his 1918 ballad about the practice:
'This patient must be now trephined,
Let all the others go;
To-morrow when the sun is up
My magic I'll them show.'
Two men the epileptic bore
And laid him on a trunk,
And when the wretch was coming round
He showed some signs of funk.
No questions put they to the man;
The doctor cleared his throat,
Then bringing flints from out his hut,
Took off his hairy coat.
A crowd had gathered all around,
To watch the bloody deed;
Their curiosity was stirred
To see his devil freed.
With sharp flint flake the surgeon made
A cruciform incision;
The blood did spurt, the wound it hurt,
The crowd laughed in derision.
The two assistants pressed the flaps
To stop the blood from running;
The Medicine-Man did scheme and plan,
He was so full of cunning.
He scraped the pericranium,
Until the skull was bare;
Then scratched the bone with a sharp stone,
It did not matter where.
He scraped that bone and scratched and scraped—
The scratches made a groove,
The groove a basin-like ellipse.
The patient did not move.
The fact was this, when he came round
So rotten did he feel,
He fainted when he found himself
The centre of such zeal.
The hollow soon became a hole,
'Twas all but through the bone,
His diploë, you well might see,
But still he made no moan.
The inner table only now
Protected his soft brain,
One final scape and he did make
That hole a window-pane.
The devil stirred within his skull
And, with a fearful yell,
Escaped from out its prison-house
To seek its own in hell.
As the poem suggests, some people believed that trepanation would release evil spirits, although historically many physicians have claimed that the procedure has some medical benefits. You can see more photos of this particular skull and its numerous holes at the Science Museum.