Common measuring mistakes
Most of these are planning errors you can catch before you cut anything.
- Forgetting wall thickness. Every wall takes one board thickness out of the space inside. Guides call this the single most-cited beginner error (The Cardboard Shelf). The designer never lets you forget it: you enter compartment sizes, and it adds every wall.
- Cutting short walls to the full outer length. With walls on the base, the short walls fit between the long walls, so they are two thicknesses shorter. The designer's reassembly check flags this.
- Forgetting the base in the height. A tray's outside height includes its base. With walls on the base, the walls are t shorter than the tray (Fractal Thought).
- Ignoring what sits on top. The rulebook, board and punchboards all take depth under the lid.
- Sizing for unsleeved cards and then sleeving them. Sleeves add about 2.5 mm to each side of the card and roughly double the stack height (see cards & sleeves).
- Trusting nominal board thickness. "5 mm" board may be 3/16 in (4.76 mm), and the reverse. Measure it (see board thickness).
- Leaning cuts. If the blade isn't vertical, the walls lean and the tray grows at the top. Stand over the work, make several light passes, and use a sharp blade and a metal ruler (The Cardboard Shelf). Expect to be up to about a millimetre out, and plan a little slack.
- Gluing in the wrong order. Don't trap a piece between two walls that are already glued. Dry-fit everything first (same source).
- Measuring from a worn ruler end or only at the box rim. Measure at the floor and use the smallest reading (see measuring).