Title Blocks, Revision Blocks, and Bills of Materials

Why Title Blocks and Bills of Materials Matter

Every structural fabrication drawing is a legal and technical document. Before you strike an arc, you must confirm you are working from the correct, current drawing and that you understand exactly what material to cut, fit, and weld. Two areas on every drawing give you that information: the title block and the bill of materials (BOM). Misreading either one can result in fabricating the wrong part, using the wrong steel, or welding to an outdated revision — all of which can cause rework, project delays, or structural failures.

The Title Block

The title block is a bordered box printed in the lower-right corner of nearly every engineering drawing. It is the first place you look before doing anything else. A standard structural steel title block contains the following fields:

• Drawing title — the name of the assembly or component (e.g., "Roof Beam — Grid Line B").
• Drawing number — a unique identifier used to order, track, and file the drawing.
• Project name and number — ties the sheet to a specific construction contract.
• Scale — the ratio between the drawn dimension and the real object (e.g., 1:10 means one inch on paper equals ten inches on the actual part). Always check scale before measuring directly off the print.
• Sheet number and total sheets — tells you how many sheets belong to this drawing set (e.g., Sheet 3 of 7).
• Drawn by / checked by / approved by — names and initials that establish accountability.
• Date — the date the drawing was originally released or last revised.
• Revision block or revision indicator — a letter or number (Rev A, Rev B, Rev C, etc.) showing which version of the drawing you hold.

Some title blocks also include the applicable code (such as AWS D1.1) and the engineer of record's stamp.

The Revision Block

Drawings change. Engineers add connections, change plate thicknesses, or move hole locations. Every change is recorded in the revision block, which is usually a small table in the upper-right corner or adjacent to the title block. Each row lists:

• The revision letter (A, B, C …).
• A brief description of what changed.
• The date the revision was issued.
• The initials of who authorized the change.

Current revision triangles or "cloud" markings may also appear on the drawing face to highlight exactly where the change was made.

Critical rule: Never fabricate from a drawing whose revision letter does not match the revision letter on the current drawing register or traveler issued by your supervisor. If the shop floor has Rev B and the engineer's office has released Rev C, work must stop on that part until the correct print is obtained and the discrepancy is documented and resolved through your company's document-control procedure.

The Bill of Materials

The bill of materials (BOM) — also called the material list or parts list — is a table found on the drawing, commonly above the title block or on a separate sheet in the set. It lists every individual piece needed to fabricate the complete assembly. For structural steel work, each row in the BOM typically includes:

• Item or part number — matches a balloon or callout on the drawing view so you can locate the part visually.
• Quantity — how many of that part are required for one complete assembly.
• Description — a brief name (e.g., "Gusset Plate", "Base Plate").
• Material specification — the ASTM designation (e.g., ASTM A36, ASTM A572 Gr 50) that defines the steel's chemistry and mechanical properties. This is not optional information — using the wrong grade can violate the engineer's design and the structural code.
• Size — dimensions such as plate thickness, width, and length, or the standard designation for rolled shapes (e.g., W8×31).
• Finish or coating notes — primer, galvanizing, or other surface treatment requirements may appear here.

When you receive a cut list or pick a plate from stock, always verify that the heat number or mill certificate for the material matches the ASTM specification shown in the BOM. AWS D1.1 requires that base metals be identified and suitable for the intended welding process.

Reading Scale Correctly

Many beginners try to measure dimensions directly off a print with a ruler. You may do this only if the drawing is printed at its stated scale and has not been reduced by a copier or plotter. If a drawing is marked "NOT TO SCALE" or "NTS," rely solely on the written dimensions. When a scale is given (e.g., 1:10), a dimension shown as 3 inches on paper represents 30 inches on the actual part.

Safety Note

Handling large-format drawings in a fabrication shop introduces its own hazards. Keep drawings away from welding arcs, grinding sparks, and hot metal — paper ignites. Store rolled prints in tubes away from compressed-gas cylinders. Never lay drawings on a welding table that may have sharp slag or hot spots. When referencing a drawing near active welding operations, wear your standard shop PPE (safety glasses, hearing protection as required) and stay clear of arc flash zones.

Connecting to the Credential Exams

NCCER Welding Level 2 (Module 29201) tests your ability to interpret title blocks and BOMs as part of blueprint reading competency. AWS SENSE Level 1–2 performance tasks require that trainees demonstrate they can read and apply information from a drawing before beginning a weld. AWS D1.1 Certified Welder qualification tests are tied to specific WPS documents that reference drawing requirements. Getting this skill right from the start is foundational to every credential you will earn in this program.