I prefer to have a few easy to tear out "sacrificial" pages at the end of my pocket notebook.
With that said, I should confess that I find it a bit maddening when I go to tear out a piece of paper from my pocket notebook and the damn rip goes all sideways
when the paper is ripped to close to the binding so that the piece of paper on the other side isn't securely attached to the notebook anymore.
My answer to this is to make my own perforated pages with a simple modification to an old fabric tracing wheel. A few lines of this sharpened wheel on a soft leather back plate perforates the paper so it can be torn out easily. This process is quick and easy to make.
Below is the fabric tracing wheel and the Japanese Saw file that I used to sharpen the teeth.
I find great enjoyment from repurposing old tools.
These Japanese saw files are great because of how thin they are. Their tapered, feathery design is perfect for getting into the small teeth of the fabric wheel. Saw files are made to be used on hardened steel.
When sharpening the teeth, I start on one side of each tooth then sharpen the other.
This double bladed tooth will keep the rip flowing in a dedicated linear movement.
A better look at the wheel so show both sides of each tooth sharpened. If one wanted to get these teeth extra smooth then you could fold some fine metal sandpaper over the file and go from there. My obsession though only goes so far as wanting the paper to easily rip out in a straight line away from the binding.
My preference for gridded paper makes this diy process even easier:
First: put a small strip of leather under the page. This lets the teeth sink more deeply into the paper.
Second: line the straight edge against the line (for field notes and done pocket notebooks is 2 grid squares in)
Third: roll the sharpened wheel about 3 times.
That is it.
Before ripping out the page just fold over to prepare the perforation for use by weakening the contact between the two sides of the sheet.