Ask where a cabinet begins and the honest answer is a stack of board. In the furniture belt of the Pearl River Delta, the usual sheet is 1220 by 2440 millimetres. Every shelf, side, door and back is a rectangle cut out of that rectangle, so the first design decision is not what the cabinet will look like — it is how little of the sheet will be wasted.
Nesting decides the dimensions
A cutting program arranges all the panels of a cabinet like a puzzle. Change a shelf from 380 to 400 millimetres and the puzzle may no longer fit; a strip of board becomes offcut. This is why so many cabinets share oddly specific depths, and why a custom size often jumps in steps rather than sliding smoothly. The machine is not refusing the request. The sheet is.
The saw kerf, the trim allowance and the grain direction all enter the same calculation. A door with the grain running the wrong way may be perfectly strong and still be rejected, because a row of doors cut from one sheet has to look like a set. The visible surface is decided in a spreadsheet.
The hole is older than the furniture
Turn a flat-pack cabinet over and you will find rows of small holes along the side panels, usually 32 millimetres apart. That spacing is a system: shelf supports, hinge plates and drawer slides all locate on the same grid. A factory can drill every panel on one machine with one setup, then assemble a shelf unit, a wardrobe or a drawer cabinet from the same drilled parts.
The grid is also why adjustable shelves are possible at all. The shelf does not need a carpenter measuring each position; it needs four pegs in four holes. Variety moves from the cutting stage to the assembly stage, which is much cheaper.
The edge is the weak point
A cut panel is ugly and vulnerable along its edge: the core is exposed, it drinks water, and it chips when a box is pushed past. Edge banding — a thin strip of PVC or veneer glued and trimmed flush — is what turns a piece of board into a usable part. Much of the cost and most of the visible quality of a cabinet sits in that few millimetres, not in the flat faces.
This is also where the shape gets constrained. A curved front, a deeply shaped edge or a mitred corner needs a different process, often a different machine, and always a slower one. The rectangle wins not because designers lack imagination but because a straight edge can be banded continuously at speed.
Why custom is fast
A made-to-measure cabinet in this system is mostly a change of parameters: a few lengths in the nesting program, a different number of holes, the same hinges and pegs. Nothing has to be retooled. What looks like a bespoke service is a very flexible way of repeating one manufacturing method.
The limits are real. Solid wood that moves with the seasons, a thick load-bearing shelf, or a joint meant to be taken apart a hundred times all ask more of the material than a banded panel comfortably gives. Read a cabinet from its edges and its holes: they tell you which decisions were made by the sheet, and which by the person who will live with it.