Everyone has a reason the fish were not biting. Almost nobody has evidence for it.

A blank gets explained on the drive home, and the explanation is nearly always the one that feels best rather than the one the day supports. The water was too clear. The pressure dropped. They were not feeding. None of those can be checked afterwards, which is exactly why they survive — and why the same blank happens again next month.

The mechanism

Ten candidate causes: location, depth, presentation, timing, water state, access, execution, tackle, effort, and the one nobody names — that you could not have known, because you were not looking. Each cause has a gate: the single observation that separates it from its nearest neighbour. Location and effort look identical from the bank; so do execution and tackle. The gate is what tells them apart, and every gate is free.

A cause is only named when its gate was actually opened. A gate you did not open leaves its cause untested — which is a different thing from ruled out, and the difference is the whole instrument. When nothing is supported it says NOT PROVEN and stops. When three or more gates came back as did not look, it says the day is not readable at all, names the nine causes that are therefore untested, and hands you the shortest list of things to observe next time that would have settled it.

Who it is for

Anyone who blanks and would rather know why than feel better about it. It works best filled in on the bank with wet hands, before memory starts editing — there is a pocket evidence card for exactly that.

Who should not buy it

If you want a reason the fish were not biting, this is the wrong purchase. Its most common finding is that the day cannot be read.

What is in it

A sixteen-question evidence run, written so that did not look is an honest and useful answer rather than an embarrassing one.
An inference engine that marks each of the ten causes supported, untested, contradicted or unsupported, holds two explanations at once when the evidence supports both, and names the test that would separate them.
All ten causes in full: what each looks like, its gate, what it gets mistaken for, what to run next trip if it is the answer, and what naming it still does not prove.
Four diagrams: the ladder and its gates, the evidence one blank actually carries, the confusion map, and four hours spent two different ways.
A pocket evidence card to fill in before you leave the water.

Format, offline and printing

Two files. The instrument itself is a single self-contained web page — it opens in any browser on any device, the brand faces are embedded in the file, and once it is on your phone it works with no signal at all. There is no app, no account and no server: everything you type stays in that browser, on that device, and you can export a JSON copy whenever you want one.

The print edition is 21 pages at US Letter, laid out for a cheap printer. The evidence card is sized to go in a pocket; the cause reference is sized to live in the box. It is readable in grayscale because nothing in it decides anything by color alone, and the type is set at field sizes rather than desk sizes.

Where it sits beside the free work

Why Didn’t It Work? and Common Situations are free and cover the doctrine. This is the instrument that applies it to one specific day and refuses to guess.

What it cannot do

It cannot tell you where the fish were. It has never seen your water and it works entirely from sixteen answers you typed. A named cause is a hypothesis with a test attached, not a finding — and the test is the part that matters.

Version 1.0 · September 2026 · Edition hth.field.blank-day-autopsy

Your purchase includes

Blank Day Autopsy — the instrument, a self-contained web page that works offline.
The Letter print edition, 21 pages, including the pocket evidence card.
Eligible corrections and updates to the same Edition, at no further cost.

You may

Read and print it on your own devices, as often as you like.
Use its methods and working pages in your own work.
If you guide, teach or work with clients: use it while serving them, and hand a client a completed output you produced with it.

You may not

Redistribute the publication, the blank working masters or the print file.
Resell or republish it, or put the complete work in a shared library or community drive.
Share your purchase credential in place of a purchase, or use the work for model-training ingestion.

Refunds

Fourteen days, no reason required. A broken, missing or materially misdescribed file is corrected or refunded without relying on that cutoff. Terms of Sale

debrief

Blank Day Autopsy