diff --git a/index.html b/index.html
index 46989d3..4772efc 100644
--- a/index.html
+++ b/index.html
@@ -74,6 +74,7 @@
               <div id="edit-fields"></div>
               <p id="edit-summary" class="muted small"></p>
               <button id="edit-regen" class="btn primary" type="button" disabled>다시 생성 · 변경 0</button>
+              <button id="edit-apply-active" class="btn-o" type="button" hidden>활성 교각에 적용</button>
             </section>
           </section>
         </aside>
diff --git a/src/core/active-piers.ts b/src/core/active-piers.ts
new file mode 100644
index 0000000..2fca62e
--- /dev/null
+++ b/src/core/active-piers.ts
@@ -0,0 +1,29 @@
+import { overrideKeys, type EditableKey, type PierValues } from './changes';
+import type { PierInput } from './types';
+
+/** One list row as the selection rules see it. */
+export interface PierSelection {
+  name: string;
+  checked: boolean;
+  hasModel: boolean;
+}
+
+/**
+ * Piers shown in the 3D view: every checked pier that has a model, plus the 기준 pier (the one whose card is open)
+ * even when it is unchecked. Order follows the list (승인 2026-10-27, 체크 = 활성).
+ */
+export function shownNames(list: PierSelection[], active: string | null): string[] {
+  return list.filter((p) => p.hasModel && (p.checked || p.name === active)).map((p) => p.name);
+}
+
+/** Piers that receive the 기준 pier's overrides: the checked piers with a model, other than the 기준 pier. */
+export function overrideTargets(list: PierSelection[], active: string | null): string[] {
+  return list.filter((p) => p.checked && p.hasModel && p.name !== active).map((p) => p.name);
+}
+
+/** The target input with the source's overridden values copied in; every other value of the target is kept. */
+export function applyOverrides(source: PierValues, target: PierInput): PierInput {
+  const next: PierInput = { ...target };
+  for (const key of overrideKeys(source) as EditableKey[]) next[key] = source.draft[key] as never;
+  return next;
+}
diff --git a/src/main.ts b/src/main.ts
index fb45f3b..89c2bbf 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -7,6 +7,7 @@ import { buildPier, type PierModel } from './core/geometry';
 import { NOT_IMPLEMENTED_RULES, validateInput, validatePier } from './core/validate';
 import { buildTemplateWorkbook } from './core/template';
 import { EDITABLE_FIELDS, FIELD_LABELS, overrideKeys, pendingKeys, revertDraft, type EditableKey, type PierValues } from './core/changes';
+import { applyOverrides, overrideTargets, shownNames, type PierSelection } from './core/active-piers';
 import { adjustRow, layoutText, resolveRowCounts, rowLayout, totalPiles } from './core/piles';
 import { applyCopy, DEFAULT_COPY_ITEMS, planCopy, type CopyItem } from './core/copy';
 import { pileGeometry } from './core/geometry';
@@ -350,13 +351,26 @@ function setView(kind: ViewKind): void {
 }
 
 /** 전체 보기 applies on ① 형상 생성 only; ③ and the others keep the single-pier scene. */
-function allViewOn(): boolean {
-  return state.allView && state.stage === 'shape';
+function selectionOf(p: Pier): PierSelection {
+  return { name: p.input.name, checked: p.checked, hasModel: p.model !== null };
 }
 
-/** Builds 전체 보기 from every pier that has a model. Returns false when none does. */
+/** The piers the 3D view shows together: the checked ones plus the 기준 pier (체크 = 활성, 승인 2026-10-27). */
+function shownPiers(): Pier[] {
+  const names = new Set(shownNames(state.piers.map(selectionOf), state.active));
+  return state.piers.filter((p) => names.has(p.input.name));
+}
+
+/** Several piers in one frame: ① 전체 보기 (button), or ② when two or more piers are shown. */
+function multiSceneOn(): boolean {
+  if (state.stage === 'shape') return state.allView;
+  if (state.stage === 'plan') return shownPiers().length >= 2;
+  return false;
+}
+
+/** Builds the shown piers in one frame. Returns false when none has a model. */
 function buildAllScene(): boolean {
-  const entries = state.piers.flatMap((p) => (p.model ? [{ name: p.input.name, model: p.model }] : []));
+  const entries = shownPiers().flatMap((p) => (p.model ? [{ name: p.input.name, model: p.model }] : []));
   if (entries.length === 0) return false;
   allPiers = buildAllPiers(entries, groundModel?.terrainGrid);
   world.add(allPiers.piers);
@@ -375,7 +389,7 @@ function setupScene(): void {
   }
   if (rebar3d) world.remove(rebar3d.group);
   rebar3d = null;
-  if (allViewOn() && buildAllScene()) {
+  if (multiSceneOn() && buildAllScene()) {
     setView(state.view);
     return;
   }
@@ -430,6 +444,7 @@ function renderPierRows(list: HTMLUListElement, mode: Stage): void {
     check.setAttribute('aria-label', `${pier.input.name} 선택`);
     check.addEventListener('change', () => {
       pier.checked = check.checked;
+      setupScene();
       renderAll();
     });
     // The pier name and type are shown here, since the 3D title band is gone on wide screens (승인 2026-10-23).
@@ -485,7 +500,8 @@ function renderInputTable(): void {
     const inp = p.input;
     const front = inp.bearings.filter((b) => b.row === '전열').length;
     const back = inp.bearings.filter((b) => b.row === '후열').length;
-    const tr = el('tr', undefined, p.input.name === state.active ? 'active' : undefined);
+    const classes = [p.checked ? 'shown' : '', p.input.name === state.active ? 'active' : ''].filter(Boolean).join(' ');
+    const tr = el('tr', undefined, classes || undefined);
     tr.tabIndex = 0;
     tr.addEventListener('click', () => selectPier(p.input.name));
     tr.addEventListener('keydown', (e) => {
@@ -533,7 +549,7 @@ function renderPanels(): void {
 
   renderInputTable();
   $('inputs-active').textContent = pier ? `활성 교각 ${pier.input.name} 상세 (표의 행을 누르면 바뀜)` : '';
-  $('edit-title').textContent = pier ? `코핑·말뚝 입력 수정 · ${pier.input.name}` : '코핑·말뚝 입력 수정';
+  $('edit-title').textContent = pier ? `코핑·말뚝 입력 수정 · 기준 ${pier.input.name}` : '코핑·말뚝 입력 수정';
 
   if (!pier) {
     fillKv($('inputs'), []);
@@ -796,6 +812,12 @@ function renderEditCard(): void {
       : '기본값과 같습니다.';
   btn.textContent = `다시 생성 · 변경 ${status.pending.length}`;
   btn.disabled = status.pending.length === 0;
+  // The 기준 pier's overrides can go to the other checked piers; they take effect on 선택 교각 다시 생성.
+  const targets = overrideTargets(state.piers.map(selectionOf), state.active);
+  const applyBtn = $<HTMLButtonElement>('edit-apply-active');
+  applyBtn.hidden = targets.length === 0;
+  applyBtn.textContent = `활성 교각 ${targets.length}기에 적용`;
+  applyBtn.disabled = overrideKeys(pier).length === 0;
 }
 
 /** One row per input key: value in the draft, the imported default beside it, and a revert button when overridden. */
@@ -1062,7 +1084,7 @@ function setStage(stage: Stage): void {
   if (stage === 'shape' && state.stage !== 'shape') state.allView = true;
   state.stage = stage;
   // Switching 전체 보기 on or off in ① needs the scene rebuilt for the new layout.
-  if ((allPiers !== null) !== allViewOn()) setupScene();
+  if ((allPiers !== null) !== multiSceneOn()) setupScene();
   if (state.scene) setRebarView(state.scene, stage === 'rebar');
   $<HTMLElement>('view-shape').hidden = stage !== 'shape';
   $<HTMLElement>('view-plan').hidden = stage !== 'plan';
@@ -3095,6 +3117,22 @@ $<HTMLButtonElement>('edit-regen').addEventListener('click', () => {
   const pier = activePier();
   if (pier) regenerateOne(pier.input.name);
 });
+
+$<HTMLButtonElement>('edit-apply-active').addEventListener('click', () => {
+  const base = activePier();
+  if (!base) return;
+  const targets = overrideTargets(state.piers.map(selectionOf), state.active);
+  const keys = overrideKeys(base);
+  if (targets.length === 0 || keys.length === 0) return;
+  const labels = keys.map((k) => FIELD_LABELS[k]).join(', ');
+  const ok = window.confirm(
+    `${targets.join(', ')}에 기준 ${base.input.name}의 ${keys.length}개 항목(${labels})을 적용합니다.\n적용 후 '선택 교각 다시 생성'을 눌러야 3D에 반영됩니다.`,
+  );
+  if (!ok) return;
+  for (const p of state.piers) if (targets.includes(p.input.name)) p.draft = applyOverrides(base, p.draft);
+  renderAll();
+  setStatus(`${targets.length}기에 ${keys.length}개 항목을 적용했습니다.`);
+});
 $<HTMLInputElement>('project-name').addEventListener('input', updateApply);
 
 $<HTMLButtonElement>('pick-file').addEventListener('click', () => $<HTMLInputElement>('file').click());
diff --git a/src/style.css b/src/style.css
index 73fc116..4cd668c 100644
--- a/src/style.css
+++ b/src/style.css
@@ -816,6 +816,7 @@ body { background: #eef1f4; font-family: 'Noto Sans KR', system-ui, sans-serif;
 #inputs-all { font-size: 12px; width: 100%; }
 #inputs-all th, #inputs-all td { white-space: nowrap; padding: 4px 6px; }
 #inputs-all tbody tr { cursor: pointer; }
+#inputs-all tbody tr.shown td { background: #f4f8fc; }
 #inputs-all tbody tr.active td { background: #e3edf8; font-weight: 700; }
 
 /* Import preview: all piers' 받침·IP rows scroll inside the dialog. */
diff --git a/tests/active-piers.test.ts b/tests/active-piers.test.ts
new file mode 100644
index 0000000..baa7767
--- /dev/null
+++ b/tests/active-piers.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect, it } from 'vitest';
+import { applyOverrides, overrideTargets, shownNames, type PierSelection } from '../src/core/active-piers';
+import { loadP1 } from './helpers';
+
+const list: PierSelection[] = [
+  { name: 'P1', checked: true, hasModel: true },
+  { name: 'P2', checked: true, hasModel: true },
+  { name: 'P3', checked: false, hasModel: true },
+  { name: 'P4', checked: true, hasModel: false },
+];
+
+describe('shownNames (체크 = 활성, 기준 교각은 항상 표시)', () => {
+  it('shows every checked pier that has a model, in list order', () => {
+    expect(shownNames(list, 'P1')).toEqual(['P1', 'P2']);
+  });
+
+  it('keeps the 기준 pier even when it is unchecked', () => {
+    expect(shownNames(list, 'P3')).toEqual(['P1', 'P2', 'P3']);
+  });
+
+  it('never shows a pier without a model', () => {
+    expect(shownNames(list, 'P4')).toEqual(['P1', 'P2']);
+  });
+
+  it('shows only the 기준 pier when nothing else is checked', () => {
+    const none = list.map((p) => ({ ...p, checked: false }));
+    expect(shownNames(none, 'P2')).toEqual(['P2']);
+  });
+});
+
+describe('overrideTargets (기준 교각의 수정 값을 받을 교각)', () => {
+  it('is the checked piers other than the 기준 pier', () => {
+    expect(overrideTargets(list, 'P1')).toEqual(['P2']);
+    expect(overrideTargets(list, 'P3')).toEqual(['P1', 'P2']);
+  });
+});
+
+describe('applyOverrides (기준 교각의 변경 항목만 옮김)', () => {
+  const base = loadP1();
+  const defaults = base;
+  const edited = { ...base, copingWidthMm: base.copingWidthMm + 100 };
+  const target = { ...base, copingLengthMm: base.copingLengthMm + 500 };
+
+  it('copies only the keys the 기준 pier overrides, keeping the target own values', () => {
+    const next = applyOverrides({ defaults, input: defaults, draft: edited }, target);
+    expect(next.copingWidthMm).toBe(edited.copingWidthMm);
+    expect(next.copingLengthMm).toBe(target.copingLengthMm);
+  });
+
+  it('returns the target unchanged when the 기준 pier has no overrides', () => {
+    const next = applyOverrides({ defaults, input: defaults, draft: defaults }, target);
+    expect(next).toEqual(target);
+  });
+});