diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c1f1c05..69208dc9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -115,6 +115,17 @@ ADR-007 and ADR-002.
 
 ### Fixed
 
+- **Ticking a section off crossed out its title and nothing else.** The strike
+  now covers everything under that heading, including its sub-sections, which
+  is what "this section is done" means to somebody who ticked the thing that
+  contained them. It needed the heading RANK, which the HTML importer was
+  discarding: every heading arrived as a sibling, so a parent had no children
+  to cross out. Headings now carry their level, render at their rank, and a
+  guide written before this reads as flat, exactly as it did. Code blocks,
+  tables and images inside a finished section are faded but not struck - a line
+  through a command makes it unreadable, and re-reading the command is usually
+  why somebody looks back at a step they have already done.
+
 - **Tech Tools was invisible to anyone without an account**, even though every
   tool on the page is deliberately usable without one and Secure Send is the
   single write this product offers a guest. The nav item named no permission,
diff --git a/docs/PROJECT-MAP.md b/docs/PROJECT-MAP.md
index d4b9857c..76390773 100644
--- a/docs/PROJECT-MAP.md
+++ b/docs/PROJECT-MAP.md
@@ -88,6 +88,6 @@ Manifest-less directories under `plugins/` are core frontend surface and always
 
 ## Size
 
-- test functions defined: **1417** (parametrised cases collect higher)
+- test functions defined: **1418** (parametrised cases collect higher)
 - documented API paths: **305** (`docs/openapi.json`, regenerate with `scripts/gen_openapi.py`)
 
diff --git a/plugins/guides/frontend/components/GuideBlocks.vue b/plugins/guides/frontend/components/GuideBlocks.vue
index b446ca12..c839a4a5 100644
--- a/plugins/guides/frontend/components/GuideBlocks.vue
+++ b/plugins/guides/frontend/components/GuideBlocks.vue
@@ -12,7 +12,8 @@
         Reading only: in the editor a tick would be an edit.
       -->
       <h2 v-if="block.type === 'heading'" :id="anchorFor(block)" class="gb-heading"
-          :class="{ 'gb-sectiondone': isTicked(block.id) }">
+          :class="['gb-h' + levelOf(block),
+                   { 'gb-sectiondone': isTicked(block.id) || inDoneSection(index) }]">
         <input v-if="interactive" type="checkbox" class="gb-sectiontick"
                :checked="isTicked(block.id)"
                :aria-label="'Mark this section done'"
@@ -21,10 +22,11 @@
       </h2>
 
       <p v-else-if="block.type === 'paragraph'" class="gb-para"
+         :class="{ 'gb-sectiondone': inDoneSection(index) }"
          v-html="inline(block.text)"></p>
 
       <div v-else-if="block.type === 'step'" class="gb-step"
-           :class="{ 'gb-sectiondone': isTicked(block.id) }">
+           :class="{ 'gb-sectiondone': isTicked(block.id) || inDoneSection(index) }">
         <label class="gb-stepnum">
           <input v-if="interactive" type="checkbox" class="gb-sectiontick"
                  :checked="isTicked(block.id)"
@@ -41,7 +43,8 @@
         editor a tick would be an edit, and an author clicking around their own
         draft would quietly change what the next reader sees as "done".
       -->
-      <ul v-else-if="block.type === 'checklist'" class="gb-checklist">
+      <ul v-else-if="block.type === 'checklist'" class="gb-checklist"
+          :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <li v-for="item in itemsOf(block)" :key="item.id" class="gb-check">
           <label>
             <input type="checkbox"
@@ -54,21 +57,25 @@
         </li>
       </ul>
 
-      <ul v-else-if="block.type === 'bullets'" class="gb-list">
+      <ul v-else-if="block.type === 'bullets'" class="gb-list"
+          :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <li v-for="item in itemsOf(block)" :key="item.id" v-html="inline(item.text)"></li>
       </ul>
 
-      <ol v-else-if="block.type === 'numbers'" class="gb-list">
+      <ol v-else-if="block.type === 'numbers'" class="gb-list"
+          :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <li v-for="item in itemsOf(block)" :key="item.id" v-html="inline(item.text)"></li>
       </ol>
 
-      <div v-else-if="block.type === 'callout'"
-           class="gb-callout" :class="'gb-' + (block.variant || 'info')">
+      <div v-else-if="block.type === 'callout'" class="gb-callout"
+           :class="['gb-' + (block.variant || 'info'),
+                    { 'gb-sectiondone': inDoneSection(index) }]">
         <strong v-if="block.title">{{ block.title }}</strong>
         <div v-html="inline(block.text)"></div>
       </div>
 
-      <div v-else-if="block.type === 'code'" class="gb-code">
+      <div v-else-if="block.type === 'code'" class="gb-code"
+           :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <div class="gb-codehead">
           <span class="gb-lang">{{ block.language || 'text' }}</span>
           <span v-if="block.caption" class="gb-caption">{{ block.caption }}</span>
@@ -108,7 +115,8 @@
         A failure says so in words. A guide whose screenshot is missing must not
         look like a guide that never had one.
       -->
-      <figure v-else-if="block.type === 'image'" class="gb-figure">
+      <figure v-else-if="block.type === 'image'" class="gb-figure"
+              :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <img v-if="imageState(block).src" :src="imageState(block).src"
              :alt="block.alt || ''">
         <p v-else-if="imageState(block).failed" class="gb-imagefailed">
@@ -118,7 +126,8 @@
         <figcaption v-if="block.caption">{{ block.caption }}</figcaption>
       </figure>
 
-      <div v-else-if="block.type === 'table'" class="gb-tablewrap">
+      <div v-else-if="block.type === 'table'" class="gb-tablewrap"
+           :class="{ 'gb-sectiondone': inDoneSection(index) }">
         <table class="gb-table">
           <thead v-if="block.header && block.header.length">
             <tr><th v-for="(cell, c) in block.header" :key="c" v-html="inline(cell)"></th></tr>
@@ -179,6 +188,42 @@ function toggle (itemid, checked) {
   emit('toggle', itemid, checked)
 }
 
+// Which heading governs each block: the nearest one above it. Ticking a
+// heading crosses off everything under it down to the next heading, because
+// that is what "this section is done" means to somebody reading - striking the
+// title alone leaves the wall of text it was introducing looking untouched.
+// Headings nest. A block belongs to every heading above it that has not been
+// closed by a heading of the same or higher rank, so ticking a top-level
+// section crosses off its sub-sections too - which is what "this section is
+// done" means to somebody who ticked the thing that contained them.
+//
+// A guide written before levels existed has none; those all read as level 2,
+// which is the flat behaviour they already had.
+function levelOf (block) {
+  const level = Number(block.level)
+  return Number.isFinite(level) && level >= 2 && level <= 6 ? level : 2
+}
+
+const ancestors = computed(() => {
+  const map = {}
+  const stack = []
+  props.blocks.forEach((block, index) => {
+    if (block.type === 'heading') {
+      const level = levelOf(block)
+      while (stack.length && stack[stack.length - 1].level >= level) stack.pop()
+      map[index] = stack.map(entry => entry.id)
+      stack.push({ id: block.id, level })
+    } else {
+      map[index] = stack.map(entry => entry.id)
+    }
+  })
+  return map
+})
+
+function inDoneSection (index) {
+  return (ancestors.value[index] || []).some(id => isTicked(id))
+}
+
 // Steps number themselves by position among steps, so inserting a paragraph
 // between two of them does not renumber anything by hand.
 const stepIndex = computed(() => {
@@ -215,11 +260,24 @@ function select (block) {
    dark mode work with no dark-mode code. */
 .gb-blocks { line-height: 1.65; }
 .gb-heading { margin: 1.6rem 0 0.6rem; font-size: 1.35rem; color: var(--text); }
+/* Rank is visible, so a reader can see what contains what - and so ticking a
+   section off looks like it covered the right amount of page. */
+.gb-h3 { font-size: 1.15rem; margin-top: 1.2rem; }
+.gb-h4, .gb-h5, .gb-h6 { font-size: 1.02rem; margin-top: 1rem; }
 
 /* A ticked section is struck through and faded, not hidden: somebody scanning
-   back up the page has to be able to read what they already did. */
+   back up the page has to be able to read what they already did.
+
+   The strike lands on the heading and on everything under it. A code block is
+   faded but NOT struck - a line through a command makes it unreadable, and the
+   reason to look back at a finished step is usually to re-read the command. */
 .gb-sectiondone { text-decoration: line-through; opacity: 0.55; }
 .gb-sectiondone .gb-stepnum { text-decoration: none; }
+.gb-code.gb-sectiondone,
+.gb-sectiondone pre,
+.gb-sectiondone code,
+.gb-figure.gb-sectiondone,
+.gb-tablewrap.gb-sectiondone { text-decoration: none; }
 .gb-sectiontick {
   /* Touch-sized: a guide is read on a shopfloor PC, often with gloves on. */
   width: 1.1rem;
diff --git a/plugins/guides/services/htmlimport.py b/plugins/guides/services/htmlimport.py
index ad90d2ed..05373839 100644
--- a/plugins/guides/services/htmlimport.py
+++ b/plugins/guides/services/htmlimport.py
@@ -244,7 +244,12 @@ class _Builder:
         if tag in ('h2', 'h3', 'h4', 'h5'):
             text = _inline(node)
             if text:
-                self._add({'type': 'heading', 'text': text})
+                # The LEVEL travels with it. Without it every heading is a
+                # sibling, and a reader who ticks a section off crosses out its
+                # title and nothing underneath - the sub-headings that belong to
+                # it look untouched, because nothing recorded that they belong.
+                self._add({'type': 'heading', 'level': int(tag[1]),
+                           'text': text})
             return
 
         if tag == 'p':
diff --git a/tests/test_plugins/test_guides_htmlimport.py b/tests/test_plugins/test_guides_htmlimport.py
index ad3bf636..e40cdbea 100644
--- a/tests/test_plugins/test_guides_htmlimport.py
+++ b/tests/test_plugins/test_guides_htmlimport.py
@@ -212,3 +212,14 @@ def test_an_empty_document_produces_a_named_guide_and_no_blocks():
     parsed = parse('')
     assert parsed['title'] == 'Untitled'
     assert parsed['blocks'] == []
+
+
+def test_a_heading_carries_its_rank():
+    """Ticking a section off has to cross out what belongs to it, and nothing
+    records that a sub-heading belongs to the heading above unless the level
+    travels with them."""
+    parsed = parse('<h1>T</h1><h2>Credentials</h2><p>Intro.</p>'
+                   '<h3>SFLD share</h3><p>Detail.</p><h2>Next</h2>')
+    headings = [(b['text'], b.get('level'))
+                for b in parsed['blocks'] if b['type'] == 'heading']
+    assert headings == [('Credentials', 2), ('SFLD share', 3), ('Next', 2)]