In a previous post Larry Caldwell says...
You might get yourself a mallet and froe and see what comes out. In the
old days, pioneers would split their own shakes any time the house
needed a roof.


Hand splitting enough shakes to do a full roof is a lot of hard work.
Might be better to take the "bolts" to a shake mill and trade them in
for already split shakes. You will have to give them some cash, but not
as much as if you bought the shakes from a lumber yard.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA