diff --git a/B06_Section/B06_Section_UI_Cross_Design_Pick.ts b/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
index a6a4c892d..1a5cf4395 100644
--- a/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
+++ b/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
@@ -522,6 +522,8 @@ export function attachDesignLinePick(input: {
     });
     layer.insertBefore(hit, firstStructureHit ?? null);
   });
+  // 암 판정 선은 보라 선 판정 아래 — 사면 발치처럼 겹친 자리는 설계선이 먼저 골라짐
+  if (rockHit && hits[0] !== rockHit) layer.insertBefore(rockHit, hits[0]);
 
   const cell = buildLineCell();
   let side: CrossSide | null = null;
diff --git a/resources/tester/helper_370_3_rock_cell.cjs b/resources/tester/helper_370_3_rock_cell.cjs
index bce0124f2..a89734c7d 100644
--- a/resources/tester/helper_370_3_rock_cell.cjs
+++ b/resources/tester/helper_370_3_rock_cell.cjs
@@ -47,8 +47,11 @@ class Node {
   append(...kids) {
     this.children.push(...kids);
   }
-  insertBefore(kid) {
-    this.children.push(kid);
+  insertBefore(kid, ref) {
+    this.children = this.children.filter((k) => k !== kid);
+    const at = ref ? this.children.indexOf(ref) : -1;
+    if (at < 0) this.children.push(kid);
+    else this.children.splice(at, 0, kid);
   }
   setAttribute(n, v) {
     this.attrs[n] = String(v);
@@ -238,13 +241,13 @@ const out = {};
 // ② 판정 선 — 점선 위 path 하나(끊긴 두 토막 · M 둘) · 보라 선 판정 클래스 · 키 rock
 {
   const c = card();
-  const index = c.hits.indexOf(c.rockHit);
   c.rockHit.click();
+  const index = c.picks[0];
   out.hit = {
     found: !!c.rockHit,
     tag: c.rockHit?.tagName,
     moves: (c.rockHit?.getAttribute("d").match(/M/g) ?? []).length,
-    last: index === c.hits.length - 1,
+    below: c.hits.indexOf(c.rockHit) === 0, // 그리는 차례 = 보라 선 판정 아래(겹친 자리는 설계선)
     picked: c.picks,
   };
   // ③ 고름 — 제목 · ▲▼↺ · ◀▶ 막음 · ▲▼ = 암만(종단으로 안 샘)
diff --git a/resources/tester/test_370_3_rock_cell.py b/resources/tester/test_370_3_rock_cell.py
index c1e579be8..c67fc3de4 100644
--- a/resources/tester/test_370_3_rock_cell.py
+++ b/resources/tester/test_370_3_rock_cell.py
@@ -42,7 +42,7 @@ def test_안_고르면_공용_칸은_암_버튼과_값(out: dict) -> None:
 def test_암_경계선_판정_선(out: dict) -> None:
     hit = out["hit"]
     assert hit["found"] and hit["tag"] == "path" and hit["moves"] == 2  # 끊긴 두 토막 한 판정
-    assert hit["last"] and hit["picked"] == [3]  # 조각 셋 뒤 · 누르면 고름
+    assert hit["below"] and hit["picked"] == [3]  # 설계선 판정 아래 · 키 차례 = 조각 셋 뒤
 
 
 def test_암_고름은_위아래만_암_키는_암만(out: dict) -> None: