Studio Matrx Monthly · Volume 1 · Issue 2 · July 2026
Amogh N P
✦ In loving memory of Amogh N P — Architect · Designer · Visionary ✦
A drafting table flat-lay — a mini-drafter, set-squares, a compass, scale and rows of pencils arranged around a blank drawing sheet, warm studio light, no people, no writing, no legible text.
Unit IInterior Graphics I

Basic Geometry & Drafting

The instruments, the lettering and the coded grammar of a sheet.

≈ 50 min + drafting platesByAmogh N P· Architect & interior designer

A technical drawing is built, not sketched by eye. Every line is constructed against a reference — the board edge, a T-square, a mini-drafter, a set-square. This unit is the discipline of the drawing office: the instruments, single-stroke lettering, sheet layout, and the coded grammar of line conventions where a thick line, a dashed line and a chain line each mean something. It is the precise counterpart to the observational Visual Arts course.

Learning objectives

By the end of this lesson, you will be able to — mapped to the course outcomes for Interior Graphics I:

1
CO1 · Understand

Identify the drafting instruments and the logic of constructing lines against references.

2
CO1 · Apply

Letter in single-stroke upright Gothic between guidelines at standard heights.

3
CO1 · Understand

Lay out a sheet — A-series size, margins and title block — and read the projection symbol.

4
CO1 · Apply

Read and draw the standard line conventions and their weight ratio, and basic constructions.

Constructed, never freehand

The instruments & the discipline

The apparatus exists so that no line is drawn by eye — and the same discipline drives the pure compass-and-set-square constructions underneath all later projection.[1, 4]

Lines are constructed against references drawing board · one true working edge T-square rides the true edge → horizontals 45° set-square 30°–60° set-square Mini-drafter two scales fixed at 90° = T-square + set-squares + protractor + scale, in one head pencils: 2H–4H light · H/HB object lines Combined set-squares give every 15° increment — never drawn by eye.
DiagramThe drafting apparatus — board, T-square, mini-drafter, set-squares and pencils, with lines constructed against references

Constructed, not freehand

The board gives one true working edge. A T-SQUARE references that edge for horizontals, or a MINI-DRAFTER (drafting machine) carries two calibrated scales at a fixed 90° and replaces the T-square, set-squares, protractor and scale in one head. SET-SQUARES (45°, and 30°–60°) ride the blade for verticals and standard angles — combined they give every 15° increment. The teaching point: lines are constructed against references, never drawn by eye.[1]

Compass & set-square only bisect an angle hexagon in a circle fillet: arc tangent to two lines These pure constructions underlie all later projection.
DiagramCompass-and-set-square constructions — bisecting an angle, a hexagon in a circle, and a fillet tangent to two lines
The coded grammar of a sheet

Lettering, layout & line conventions

Single-stroke lettering, the ISO sheet and its title block, and the line conventions that carry meaning by type and weight.[1, 2, 3]

Single-stroke, upright, uppercase Gothic cap line base line ABCD 123 height h (nominal series: 2.5 · 3.5 · 5 · 7 · 10 · 14 · 20 mm) One pass per stroke — uniform width Word gap ≈ one letter “O” Not: cursive, serif or sloping Not: personal flourish over legibility Consistency and legibility over style — always between light guidelines.
DiagramSingle-stroke upright Gothic lettering drawn between cap and base guidelines at the standard height series
Sheet layout — A-series, margin, title block A1A2A3A4 Each size = half the area above · A0 = 841 × 1189 mm ≈ 1 m² binding margin (~20–25 mm) TITLE BLOCK title · scale · date · symbol Title block bottom-right; wider margin on the left for filing.
DiagramSheet layout — the ISO A-series sizes nested, the left binding margin, and the title block bottom-right

Single-stroke upright Gothic

'Single-stroke' means each stroke is one pass of the pencil at uniform width — not built up like calligraphy. The standard is UPPERCASE, vertical (upright), Gothic (sans-serif), uniform: consistency and legibility over personal style, always drawn between light guidelines (at least a cap line and a base line). Nominal heights follow a preferred series — 2.5, 3.5, 5, 7, 10, 14, 20 mm; notes and dimensions ~2.5–3.5 mm, titles larger. Word spacing ≈ one letter 'O'; line spacing generous so dimensions do not collide.[1, 2]

Line type is a code, not decoration Continuous thick → visible edges Continuous thin → dimension, hatch, leader Dashed → hidden edges Long chain thin → centre lines & axes Chain thick → cutting plane (A–A) Thin wavy → break line Weight ratio thin : thick ≈ 1 : 2 — a thick line means “visible edge”, not merely “darker”.
DiagramThe standard line conventions — visible, dimension, hidden, centre, cutting-plane and break lines and their meanings
Read the code

Try it — the line-convention explorer

Pick a line type to see it drawn at its true weight and dash, and what it means on a drawing.

Line-convention explorer · read the code

Continuous thick

Means
Visible outlines and object edges
Weight
Thick — the widest line on the sheet.

Every edge of the object you can actually see from this view.

Line type and weight are a code — a thick line means “visible edge”, not merely “darker”.

Myth vs reality

At a glance

AspectOne sideThe other
How a line is madeMyth: drawn by eyeReality: constructed against a reference edge
LetteringMyth: any neat style is fineReality: single-stroke, upright, uppercase Gothic
Line weightMyth: thicker = just darkerReality: weight is a semantic code
Construction linesMyth: as dark as object linesReality: very light (2H–4H), left on the sheet
Title block & borderMyth: freehand, anywhereReality: ruled; block bottom-right, margin left
Vocabulary

Key terms

Mini-drafter

A drafting machine with two scales fixed at 90° — replaces T-square, set-squares, protractor and scale.

Single-stroke lettering

Each stroke is one uniform-width pass — upright uppercase Gothic, drawn between guidelines.

A-series sizes

ISO sheets, each half the area of the one above: A0 (1 m²) down to A4 (210 × 297 mm).

Title block

The bottom-right box carrying title, scale, sheet number, date and the projection symbol.

Line convention

The coded grammar of line type and weight — visible, hidden, centre, dimension, cutting, break.

Fillet / tangent

An arc drawn tangent to two lines (or a line and a circle) by compass construction.

Apply it

Drafting plate

On one A3 sheet: (a) letter the single-stroke upright Gothic alphabet A–Z and 0–9 at 5 mm then 3.5 mm between guidelines; (b) draw and label each standard line type at its correct relative weight; and (c) construct, by compass and set-square only, a bisected angle, a regular hexagon in a circle, and a fillet tangent to two lines. Add a ruled border and a title block with the projection-symbol box.

Check your understanding

Self-assessment

1. The standard for technical lettering is —

2. A dashed line on a drawing means —

3. An A0 sheet has an area of —

In a nutshell

Recap

Every line is constructed against a reference (board edge, T-square, mini-drafter, set-square) — never drawn by eye.
Letter in single-stroke, upright, uppercase Gothic between guidelines, at the standard height series.
Lay the sheet out to the ISO A-series with a left binding margin and a bottom-right title block carrying the projection symbol.
Line type and weight are a code: thick visible, thin dimension, dashed hidden, chain centre/cutting, wavy break — weight ratio ≈ 1:2.
Compass-and-set-square constructions (bisections, polygons, tangents) underlie all later projection.
The evidence

References & further reading

  1. [1]N.D. Bhatt & V.M. Panchal, Engineering Drawing, Charotar Publishing (lettering, lines, instruments, constructions).
  2. [2]BIS SP 46: Engineering Drawing Practice for Schools and Colleges — Indian line, lettering and layout conventions (IS 9609 lettering, IS 10714 lines, IS 10711 sheet sizes; confirm current BIS number).
  3. [3]Francis D.K. Ching, Architectural Graphics, Wiley (sheet composition, line weights, drafting fundamentals).
  4. [4]I.H. Morris, Geometrical Drawing for Art Students (bisections, polygons, tangents, loci).

Further reading

  • N.D. Bhatt & V.M. Panchal — Engineering Drawing.
  • Francis D.K. Ching — Architectural Graphics.
  • BIS SP 46 — Engineering Drawing Practice for Schools and Colleges.

Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.

A

The author

Amogh N P

Architect, interior designer, and creative polymath. Studio Matrx began in his notebooks — his vision of design made honest, useful, and open to everyone. Its Academy is written and taught in his memory, and free, forever.

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