diff --git a/src/view/abut-scene.ts b/src/view/abut-scene.ts
index 91047f5..98e46d6 100644
--- a/src/view/abut-scene.ts
+++ b/src/view/abut-scene.ts
@@ -79,6 +79,23 @@ function toAxis(model: AbutModel, p: AbutPoint): { s: number; t: number } {
   return { s: d.e * model.u.e + d.n * model.u.n, t: d.e * front.e + d.n * front.n };
 }
 
+/** Keeps the part of a 2-D profile where g(x, y) ≥ 0 (Sutherland–Hodgman; g is linear, so the cut is a straight line). */
+function clipByLine(poly: [number, number][], g: (x: number, y: number) => number): [number, number][] {
+  const out: [number, number][] = [];
+  for (let i = 0; i < poly.length; i++) {
+    const p = poly[i];
+    const q = poly[(i + 1) % poly.length];
+    const gp = g(p[0], p[1]);
+    const gq = g(q[0], q[1]);
+    if (gp >= 0) out.push(p);
+    if (gp * gq < 0) {
+      const f = gp / (gp - gq);
+      out.push([p[0] + (q[0] - p[0]) * f, p[1] + (q[1] - p[1]) * f]);
+    }
+  }
+  return out;
+}
+
 /** Keeps the part of a 2-D profile with x ≥ x0 (Sutherland–Hodgman against one line). */
 function clipBelowX(poly: [number, number][], x0: number): [number, number][] {
   const out: [number, number][] = [];
@@ -255,9 +272,18 @@ export function buildAbutGroup(
       ...[...wing.bottomLine].reverse().map((p) => [p.dM, p.el] as [number, number]),
     ];
     const ax = new THREE.Vector3(dir.ws, 0, dir.wt);
-    // The wing starts behind the 벽체 back face (t = 벽체 배면 −0.8): the part in front of it lies inside the 벽체 and 흉벽, so it is cut off.
-    const geom = prism(clipBelowX(profile, members.shape.wallBackM / dir.wt), 0.45, new THREE.Vector3(sEnd, 0, 0), ax, ey, new THREE.Vector3(a, 0, 0));
-    add('wings', geom, 0xc9a77c);
+    // 삽도 (A-A, 평면): above the 브라켓 상면 the wing meets the 흉벽 back face (t = −0.5); below it, the wing meets the 벽체 back face (t = −0.8).
+    // The part in front of those faces lies inside the 벽체 or 흉벽, so it is cut off. The bracket falls along s, so the cut follows it.
+    // The wing is 0.45 thick along s, so its footprint spans two s values at each dM; the cut uses the end where the 브라켓 is highest.
+    const slopeS = (members.parapetTopEndEl - members.parapetTopStartEl) / L;
+    const highEnd = slopeS < 0 ? Math.min(0, a * WING_THICKNESS_M) : Math.max(0, a * WING_THICKNESS_M);
+    const bracketAtDm = (dM: number) => members.parapetTopStartEl + slopeS * (sEnd + dir.ws * dM + highEnd) - members.shape.bracketHeightM;
+    const above = clipByLine(profile, (x, y) => y - bracketAtDm(x));
+    const below = clipByLine(profile, (x, y) => bracketAtDm(x) - y);
+    const upper = prism(clipBelowX(above, members.shape.parapetBackM / dir.wt), WING_THICKNESS_M, new THREE.Vector3(sEnd, 0, 0), ax, ey, new THREE.Vector3(a, 0, 0));
+    const lower = prism(clipBelowX(below, members.shape.wallBackM / dir.wt), WING_THICKNESS_M, new THREE.Vector3(sEnd, 0, 0), ax, ey, new THREE.Vector3(a, 0, 0));
+    add('wings', upper, 0xc9a77c);
+    add('wings', lower, 0xc9a77c);
     for (const h of wing.haunches) {
       const shape: [number, number][] = h.corners.map((c) => {
         const p = toAxis(model, c);
diff --git a/tests/abut-blocks-slab.test.ts b/tests/abut-blocks-slab.test.ts
index 06d26db..d6a337c 100644
--- a/tests/abut-blocks-slab.test.ts
+++ b/tests/abut-blocks-slab.test.ts
@@ -69,7 +69,7 @@ describe('교대 3D: 받침블럭과 접속슬래브 (spec §4.2, §4.8)', () =>
     expect(Math.min(...backs)).toBeCloseTo(members.shape.wallBackM, 6);
   });
 
-  it('the 날개벽 stays behind the 벽체 back face, so it does not enter the 벽체 or the 흉벽', () => {
+  it('the 날개벽 meets the 흉벽 back face above the 브라켓 and the 벽체 back face below it, and never enters them', () => {
     // All 벽체 and 흉벽 parts lie at t ≥ 벽체 배면 (−0.8). A wing vertex with t ≤ −0.8 therefore has no volume in common with them.
     const z = (g: THREE.Object3D) => {
       const pos = (g as THREE.Mesh).geometry.getAttribute('position');
@@ -77,7 +77,15 @@ describe('교대 3D: 받침블럭과 접속슬래브 (spec §4.2, §4.8)', () =>
       for (let i = 0; i < pos.count; i++) max = Math.max(max, pos.getZ(i));
       return max;
     };
-    for (const w of (named('wings') as THREE.Group).children) expect(z(w)).toBeLessThanOrEqual(members.shape.wallBackM + 1e-6);
+    // Upper part (above the 브라켓 상면) meets the 흉벽 back face (−0.5); the lower part meets the 벽체 back face (−0.8).
+    const backTop = (s: number) => members.parapetTopStartEl + ((members.parapetTopEndEl - members.parapetTopStartEl) * s) / model.length - members.shape.bracketHeightM;
+    for (const w of (named('wings') as THREE.Group).children) {
+      expect(z(w)).toBeLessThanOrEqual(members.shape.parapetBackM + 1e-6);
+      const pos = (w as THREE.Mesh).geometry.getAttribute('position');
+      for (let i = 0; i < pos.count; i++) {
+        if (pos.getZ(i) > members.shape.wallBackM + 1e-6) expect(pos.getY(i)).toBeGreaterThanOrEqual(backTop(pos.getX(i)) - 1e-6);
+      }
+    }
     for (const w of (named('wall') as THREE.Group).children) expect(new THREE.Box3().setFromObject(w).min.z).toBeGreaterThanOrEqual(members.shape.wallBackM - 1e-6);
   });
 
diff --git a/tests/abut-scene.test.ts b/tests/abut-scene.test.ts
index 316288d..3c97686 100644
--- a/tests/abut-scene.test.ts
+++ b/tests/abut-scene.test.ts
@@ -26,7 +26,7 @@ describe('교대 A1 3D 장면 (AA3·AA3b·AA3c)', () => {
     expect(count('parapet')).toBe(10); // per step: back strip (흉벽 배면 단차) and the 흉벽 (삽도)
     expect(count('footing')).toBe(1);
     expect(count('piles')).toBe(18);
-    expect(count('wings')).toBe(2);
+    expect(count('wings')).toBe(4); // upper and lower part per wing
     expect(count('haunches')).toBe(4);
   });