SKILL

Container Lines

Add vertical container-size guide lines with mini corner squares for precise, structured web layouts. Use when asked for container lines, measured layout guides, vertical boundary lines, editorial grid markers, or small corner-square frame details.

● INSTALL

This skill ships inside the skills package. Install the package to get this skill plus everything else in the bundle.

sv install mengto/skills

● SKILL.MD

Container Lines

Use When

A page needs subtle vertical guides that reveal the content container width.
A hero, section, or product page feels too loose and needs structural tension.
The design calls for mini corner squares, measured edges, or quiet technical framing.

Rules

Draw lines at the left and right edges of the main content container.
Keep lines thin: 1px with low opacity.
Add mini squares at container corners or section intersections.
Keep the line system consistent across sections; do not change width per section.
Place lines behind content but above the page background.
Disable pointer events so the guides never block UI.

Base Tokens

css

:root {
  --container-max: 1120px;
  --container-pad: clamp(20px, 4vw, 48px);
  --line-color: rgba(24, 24, 27, 0.14);
  --line-strong: rgba(24, 24, 27, 0.28);
  --corner-size: 6px;
}

Page Container Lines

Use pseudo-elements on the layout shell.

css

.container-lines {
  position: relative;
  isolation: isolate;
}

.container-lines::before,
.container-lines::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  z-index: -1;
  width: 1px;
  background: var(--line-color);
  pointer-events: none;
}

.container-lines::before {
  left: max(var(--container-pad), calc((100vw - var(--container-max)) / 2));
}

.container-lines::after {
  right: max(var(--container-pad), calc((100vw - var(--container-max)) / 2));
}

Corner Squares

Add four small squares to sections that need a precise measured feel.

css

.corner-squares {
  position: relative;
}

.corner-squares > .corner {
  position: absolute;
  width: var(--corner-size);
  height: var(--corner-size);
  background: var(--line-strong);
  pointer-events: none;
}

.corner.top-left { top: 0; left: 0; transform: translate(-50%, -50%); }
.corner.top-right { top: 0; right: 0; transform: translate(50%, -50%); }
.corner.bottom-left { bottom: 0; left: 0; transform: translate(-50%, 50%); }
.corner.bottom-right { right: 0; bottom: 0; transform: translate(50%, 50%); }

html

<main class="container-lines">
  <section class="corner-squares">
    <span class="corner top-left"></span>
    <span class="corner top-right"></span>
    <span class="corner bottom-left"></span>
    <span class="corner bottom-right"></span>
    ...
  </section>
</main>

Minimal Section Wrapper

Use the same container width as the line positions.

css

.content-container {
  width: min(100% - (var(--container-pad) * 2), var(--container-max));
  margin-inline: auto;
}

Taste Rules

Use lines as structure, not decoration. They should organize the page quietly.
Do not add lines to every nested component; keep them at page or major-section level.
Mini squares should be small and exact, usually 4px to 8px.
Avoid bright accent colors unless the entire visual system is technical or industrial.
Keep container max-width and padding shared between content and guide lines.

Quick Checks

The vertical lines align exactly with the content container edges.
Corner squares sit on real container or section corners, not arbitrary positions.
Lines remain subtle on light and dark backgrounds.
Mobile still has enough padding between the line and content.
Guides do not intercept clicks, hovers, or text selection.