Key terms explained: items, BOMs, works orders and stock

Manufacturing vocabulary is unusually slippery: every shop uses the same words slightly differently, and half of them are used loosely in conversation and precisely in software. This page pins down the eight that matter. If you read nothing else first, read this.

Anything you buy, make, hold or sell. One item, one record — a raw sheet, a machined part, a finished product and a box are all items.

The distinction people get wrong: an item is not a stock figure. The item is the definition (what it is, what it costs, who supplies it). The stock is a separate fact about how many exist and where. One item can have stock in four places, or none at all, and still be perfectly valid.

The recipe: which items, and how many of each, go into making one of something else. An item with a BOM is usually called an assembly.

The distinction people get wrong: a BOM is a list of ingredients, not a set of instructions. "Two brackets and four bolts" is the BOM. "Fit the brackets before you torque the bolts" is a work instruction. Keeping them apart matters, because the recipe changes when engineering changes, and the method changes when the shop finds a better way. Those are different events with different approvals.

BOMs nest. An assembly can contain assemblies, several levels deep, and the system follows the whole tree when it works out what a job needs.

The instruction to actually make something: this assembly, this quantity, by this date. It is the unit of work the shop floor sees, and the thing costs get attached to.

The distinction people get wrong: a works order is not a sales order. A sales order is a promise to a customer. A works order is a decision to build. Often one causes the other, but not always — you might build to stock with no customer in sight, or fill an order from stock without building anything.

These three numbers are the heart of the whole thing, and confusing them causes more trouble than any other misunderstanding in this list.

• On hand — physically present. What you would find if you counted.
• Allocated — physically present but already promised to a job or an order. Still on the shelf; not yours to spend.
• Available — on hand minus allocated. The only one of the three that answers "can I commit this to something new?"

A spreadsheet almost always tracks on hand and calls it availability. That single conflation is the most common cause of a shortage discovered too late.

Where stock physically is — a warehouse, an aisle, a rack, a bin. Locations exist so that "we have it" can be followed by "it is in F-04-2" rather than a search.

The distinction people get wrong: detail costs discipline. Bin-level locations are only worth having if movements are actually recorded when things move. If they are not, a precise location is worse than a vague one, because it is confidently wrong. Start coarse and tighten later.

Both answer "which specific ones". A lot (or batch) identifies a group made or received together. A serial number identifies one individual unit.

You want one or the other when a defect needs to be traced — to know which customers received material from the bad batch, and which did not. Lots suit material bought and consumed in quantity; serials suit units with a service life. Tracking everything both ways is a common early mistake and mostly buys you data entry.

The act of reserving stock for a particular job or order. Allocation is what turns a shared pool into a set of commitments, and it is what makes the available figure trustworthy.

It is also the step people skip when they are in a hurry — taking material for a rush job without recording it. Do that a few times and every number downstream becomes fiction.

A work centre is where work happens — a machine, a bench, a cell, a team. A routing is the sequence of operations a job passes through, and how long each takes.

Routings are what let the system answer "when can this realistically be finished", because capacity is finite. A shop with no routings can still track material perfectly well; it just cannot promise dates with any confidence.

In one sentence: a customer order creates demand for an item; the item's BOM says what that demand needs underneath it; stock and allocation say how much of that you already have free; purchasing covers the gap; a works order turns material into the finished item along a routing; and lots or serials record which specific ones went where.

Every screen in Brytebuild is one step in that loop. If a page ever seems arbitrary, it is worth finding which part of this sentence it belongs to.

What's next