Parts catalog terms, defined

An illustrated parts catalog (IPC) is a manufacturer's reference that pairs exploded-view drawings of a machine with the part numbers, descriptions, and quantities needed to identify and order each serviceable part. An illustrated parts catalog is organized by system and assembly, such as axles, brakes, and lighting on a trailer or booms and hydraulics on a crane. The full explanation is in What is an illustrated parts catalog?

An exploded view is a drawing of an assembly pulled apart along its axes, with each component separated slightly from its neighbors so every piece is visible in the order it fits together. In a parts catalog, the exploded view of a brake chamber and slack adjuster lets a technician point to the exact clevis pin, washer, or bracket they need instead of trying to describe it over the phone.

A callout number is the label on an exploded-view drawing that points to one component and links it to a row in the parts table. That row gives the part number, description, quantity per assembly, and notes on where the part applies. Callout numbers are local to a drawing: callout 7 on the landing gear page and callout 7 on the lighting page are unrelated parts.

A manufacturing bill of materials (MBOM) is the list of everything the factory uses to build a unit: purchased components, fabricated parts, raw stock, consumables, and the subassemblies they form, structured the way production needs them. The MBOM is built for the plant floor, not the parts counter, so it includes many items that are never sold as service parts. From manufacturing BOM to service parts catalog covers how one becomes the other.

An engineering bill of materials (EBOM) is the product structure as designed, usually maintained in the engineering team's CAD and product data systems. The EBOM organizes parts by function and design intent rather than by how the plant assembles them. The EBOM changes through engineering change orders, and those changes flow downstream into the manufacturing bill of materials and, eventually, into the parts catalog.

A service bill of materials (service BOM or SBOM) is the version of the build data that supports maintenance and parts sales. A service BOM keeps the serviceable parts, groups them the way a technician replaces them, adds kits and supersessions, and drops items such as weld wire, paint, and internal fabrication steps. The service BOM is the data a parts catalog is built on.

A serviceable part is a component a dealer or fleet can order and replace in the field. A brake chamber, a marker lamp, or a door hinge is serviceable; the steel plate a crossmember is cut from is not. Deciding which items in the build data are serviceable is one of the main jobs in creating a catalog, covered in Which parts are serviceable?

An assembly is a group of parts joined to perform one function, such as a hub-and-drum assembly, a hydraulic cylinder, or a rear door. In a parts catalog, an assembly can be sold whole, broken into individually orderable components, or both. Whether a technician replaces the whole assembly or a single seal inside it determines how the catalog should present the assembly.

A kit is a set of parts sold together under one part number because they are replaced together. A brake reline kit with shoes, springs, and hardware, or a seal kit for an outrigger cylinder, saves the counter from looking up each piece and makes sure the technician has everything for the job. Kits usually exist only in the service world and do not appear in the manufacturing bill of materials.

A supersession is the record that one part number has been replaced by another. Supersessions happen when a supplier discontinues a component, engineering improves a design, or two parts are consolidated into one. A catalog that tracks supersessions sends a lookup for the old number to the current one, so a dealer never quotes a part that can no longer be bought.

A cross-reference, also called an interchange, maps one part number to equivalent numbers from other sources: the OEM's number, the original supplier's number, and aftermarket numbers for parts that fit the same application. Counter staff rely on a cross-reference when a customer arrives with the number stamped on the old part rather than the OEM part number. Unlike a supersession, a cross-reference does not mean the original number was retired.

An as-built configuration is the exact list of parts a specific unit was built with, including the options chosen and the engineering changes in effect on its build date. Two trailers sold under the same product name can differ in axle package, suspension, lighting harness, and door hardware. The as-built record is what lets a catalog answer for one serial number instead of a whole product line.

A vehicle identification number (VIN) is the 17-character code assigned to on-road equipment such as trucks, trailers, and fire apparatus. The VIN identifies the manufacturer, the vehicle type, the production year, the plant, and a sequential number for the individual unit. In a parts catalog, the VIN is the most reliable key for pulling up the as-built configuration of a specific trailer or truck.

A serial number is the manufacturer's unique identifier for one unit, used where a VIN does not apply or alongside one. Cranes, agricultural implements, and fire apparatus pumps all carry serial numbers, as do many major components such as axles and hydraulic pumps. Catalogs often note serial ranges, such as "serial 4120 and later," to show where a part change took effect.

An OEM part is supplied by or through the original equipment manufacturer and matches the specification the unit was built to. An aftermarket part is made or sold by a third party to fit the same application. Aftermarket parts can be equivalent, cheaper, or easier to get, but they may not match the original specification, and each one sold is a sale the manufacturer did not make.

Fitment is whether a part fits and functions on a specific unit. A lighting harness can share a connector with the correct one and still be the wrong length for a 53-foot trailer. Fitment data ties each part to the units, serial ranges, and configurations it applies to, so a lookup returns parts that fit the machine in the bay rather than parts that fit something similar.

A dealer management system (DMS) is the software a dealership runs on: parts inventory, counter sales, service work orders, invoicing, and accounting. Parts staff spend most of the day in the dealer management system, so a parts catalog that hands its results into the DMS saves the counter from retyping part numbers and quantities between screens.

A parts portal is a manufacturer's website where dealers, and sometimes fleets, look up parts, check availability, and place orders. Most heavy-duty dealers carry several brands and so work across several parts portals, each with its own login, search, and ordering flow. A parts portal is only as useful as the catalog data behind it.