diff --git a/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailItem.razor b/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailItem.razor
new file mode 100644
index 0000000..28e87f6
--- /dev/null
+++ b/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailItem.razor
@@ -0,0 +1,12 @@
+@* Components/NavRailItem.razor *@
+<NavLink class="rail-link" href="@Href" Match="@Match" ActiveClass="active">
+    @if (Icon is not null) { <span class="rail-ico">@Icon</span> }
+    @Text
+</NavLink>
+
+@code {
+    [Parameter, EditorRequired] public string Href { get; set; } = string.Empty;
+    [Parameter, EditorRequired] public string Text { get; set; } = string.Empty;
+    [Parameter] public RenderFragment? Icon { get; set; }
+    [Parameter] public NavLinkMatch Match { get; set; } = NavLinkMatch.Prefix;
+}
diff --git a/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailSection.razor b/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailSection.razor
new file mode 100644
index 0000000..eb5bd5d
--- /dev/null
+++ b/ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/NavRailSection.razor
@@ -0,0 +1,12 @@
+@* Components/NavRailSection.razor — CSS-only collapsible (no JS, works in static SSR).
+   Apps that want cookie-persisted expand state keep their own interactive NavSection. *@
+<details class="rail-section" open="@Expanded">
+    <summary class="rail-eyebrow-toggle"><span class="rail-eyebrow-label">@Title</span></summary>
+    <div class="rail-section-body">@ChildContent</div>
+</details>
+
+@code {
+    [Parameter, EditorRequired] public string Title { get; set; } = string.Empty;
+    [Parameter] public bool Expanded { get; set; } = true;
+    [Parameter] public RenderFragment? ChildContent { get; set; }
+}
diff --git a/ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/NavRailTests.cs b/ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/NavRailTests.cs
new file mode 100644
index 0000000..3e6ec95
--- /dev/null
+++ b/ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/NavRailTests.cs
@@ -0,0 +1,27 @@
+namespace ZB.MOM.WW.Theme.Tests;
+
+public class NavRailTests : TestContext
+{
+    [Fact]
+    public void NavRailItem_renders_rail_link_with_href_and_text()
+    {
+        var cut = RenderComponent<NavRailItem>(p => p
+            .Add(x => x.Href, "/clusters")
+            .Add(x => x.Text, "Clusters"));
+        var a = cut.Find("a.rail-link");
+        Assert.Equal("/clusters", a.GetAttribute("href"));
+        Assert.Contains("Clusters", a.TextContent);
+    }
+
+    [Fact]
+    public void NavRailSection_renders_title_and_children_open_by_default()
+    {
+        var cut = RenderComponent<NavRailSection>(p => p
+            .Add(x => x.Title, "Navigation")
+            .AddChildContent("<a class='rail-link'>X</a>"));
+        var details = cut.Find("details.rail-section");
+        Assert.True(details.HasAttribute("open"));
+        Assert.Contains("Navigation", cut.Find("summary").TextContent);
+        Assert.NotNull(cut.Find(".rail-section-body .rail-link"));
+    }
+}