diff --git a/resources/views/rd/fire-shutter-drawing/index.blade.php b/resources/views/rd/fire-shutter-drawing/index.blade.php
index cab35de9..e60a30d4 100644
--- a/resources/views/rd/fire-shutter-drawing/index.blade.php
+++ b/resources/views/rd/fire-shutter-drawing/index.blade.php
@@ -1394,9 +1394,8 @@ function renderSbSide() {
                 return `
                     <!-- 케이스 외부: 슬랫 하강 -->
                     <line x1="${railCx}" y1="${oy+sH}" x2="${railCx}" y2="${oy+sH+20}" stroke="#f59e0b" stroke-width="2" stroke-dasharray="5 3" opacity="0.5"/>
-                    <!-- 케이스 내부: 레일홀에서 수직 상승 → 샤프트 근처에서 롤 좌측으로 (팽팽한 천) -->
-                    <line x1="${railCx}" y1="${oy+sH-vt}" x2="${railCx}" y2="${shaftCy+rollR}" stroke="#f59e0b" stroke-width="2.5" stroke-dasharray="5 3" opacity="0.5"/>
-                    <line x1="${railCx}" y1="${shaftCy+rollR}" x2="${shaftCx-rollR*0.85}" y2="${shaftCy+rollR*0.45}" stroke="#f59e0b" stroke-width="2.5" stroke-dasharray="5 3" opacity="0.5"/>
+                    <!-- 케이스 내부: 레일홀에서 샤프트 롤 좌측까지 대각선 직선 (팽팽한 천) -->
+                    <line x1="${railCx}" y1="${oy+sH-vt}" x2="${shaftCx-rollR}" y2="${shaftCy}" stroke="#f59e0b" stroke-width="2.5" stroke-dasharray="5 3" opacity="0.5"/>
                     <text x="${railCx+12}" y="${oy+sH+18}" fill="#94a3b8" font-size="8" font-weight="700" font-family="Pretendard">↓ 슬랫</text>
                 `;
             })()}