Puzzle

[NCArcher]

Somebody please solve this.
My brain hurts. I've tried for an hour last night before I gave up.

https://www.theguardian.com/science/...-brain-in-half

EDIT: Just discovered the solution has been posted but challenge yourself and don't cheat.
I was on the right track but didn't get there.

[Wongo]

It is too hard. I need to go upSTAIRS to have a rest.

[rrich]

It is too hard. I need to go upSTAIRS to have a rest.

But that is the clue to the solution.

[Allan at Wallan]

I STARED at it for a while before looking at
the solution. Got to admit I would never have worked it out.
Well done!

[Christos]

I think the use of that particular saw is deceptive.